>> this is "bbc world news america." >> funding of this presentation is made possible by the freeman foundation and kovler foundation, pursuing solutions for america's neglected needs. >> planning a vacation escape that is relaxing, inviting, and exciting is a lot easier than you think. you can find it here in aruba. families, couples, and friends can all find their escape on the island with warm sunny days, cooling trade winds, and the

crystal blue caribbean sea. nonstop flights are available from most major airports. more information for your vacation planning is available at aruba.com. >> and now, "bbc world news." jane: this is "bbc world news america," i'm jane o'brien. the threat level in britain is raised to critical after a bomb partially explodes. witnesses described the scene. >> massive bang occurred. looked around. the first thing we saw was a red-orange fire wall. >> the fire was going over your head and everybody screaming. you just run out of the tube. jane: the u.n. security council discusses north korea's latest missile launch. in japan, the sound of sirens is becoming all too familiar.

>> the people who live here in towns and cities along the coast, the second time that has happened in less than three weeks. jane: it is the end of a mission in space. for more than a decade, the cassini probe circle saturn and now it is consumed by the planet itself. ♪ jane: tonight the threat level , in britain has been raised from severe to critical after a bomb partially exploded on a tube train. authorities are calling it a terrorist incident. luckily, no one was killed but 29 people have been treated in hospital. the bbc has learned above the bomb described as a homemade

device was fitted with a timer that failed to detonate. the search continues for the person who planted it. lucy: on the floor of the tube, still in flames, it was supposed to blow up the carriage. it caused panic, fear, some injuries but thankfully it did not kill. at 20 past 8:00 this train had just arrived at parsons green. >> it was loud enough to make they wonder what the bang was. this wall of fire was coming towards use. >> i turned left and i saw the fire ball. lucy: luke was in the carriage listening to music. >> flash to my left. almost immediately. a surge of people screaming and running towards me. lucy: the improvised bomb was in a white bucket with wires attached in a freezer bag.

david nelson saw it partially detonate. >> children on the way to school. a flash of light in the carriage. felt the heat waves and a burst of flames. panic. everyone pushing to get off. luckily the doors were open. into the station. and then, the chaotic, people being thrown everywhere, people being trampled. >> it was people running over other people within the carriage. when i got outside the trainer -- i was able to see people jumping off the train station towards the end of the carriage. lucy: passengers on the train behind were helped down the tracks. children had their school journey interrupted in the most frightening manner. within minutes armed police, fire crews and eminences -- and ambulances arrived.

it was clear there were some injuries. >> no one is allowed to hear. -- through here. lucy: burns and from the stampede after, 30 taken to hospital. this woman whose commute to work ending in a different way -- relieved to be safe. peter suffered burns to his head. >> there was a fireball above my head. and there was a lot of people with facial burns and since hair -- singed hair. worst casualty, a gentleman had a puffer jacket, that melted at the back -- lucy :a large area has been cordoned off and this afternoon the police announced they were evacuating local residents living closest to it to allow them to try and make that device more stable. as so-called islamic state said it carried out the attack, police hunted for the would-be bomber and the terror threat

level to the u.k. was raised. >> the joint terrorism analysis center, the independent organization responsible for setting the threat level on the basis of available intelligence has now decided to raise the national threat level from severe to critical. this means that their assessment is that a further attack may be imminent. lucy: the army were replaced police officer's at some locations as hundreds of detectives search for who planted this bomb. >> we are making excellent progress, to identify, to locate and arrest those responsible. and this is a very complex investigation which is continuing at speed with the full weight of the london counterterrorism policing resources. my colleagues around the country and by our intelligence agency partners such as mi-5. lucy: for those who walked out of the tube carriage today there is relief.

>> lucky. i can give my wife and kids a big cuddle tonight. happy to be here. lucy: but with a bomber on the run and fears another attack could be imminent, these are tense times for those whose job it is to catch him. jane: the head of counterterrorism and the u.k. says hundreds of detectives are now involved in the investigation. the bomb is being examined by forensic teams and they are looking through cctv for clues. our security correspondent gordon -- takes a closer look at the investigation and where it might lead. gordon: the device at the heart of the investigation. the ongoing hunt for the person who planted it has now led to the u.k.'s threat level moving to critical, the highest level. the makeshift bomb will have yielded some clues in that hunt,

like these wires coming from the bucket used to trigger an explosion. they look similar to these christmas tree lights that a birmingham man plan to use in a homemade device before he was arrested. such improvised devices do not always go off properly. that was the case on july 21, 2005. and experts believe today's bomb also did not explode as intended. >> the device that was employed was quite -- and had that device functioned in its intended mode, we have seen considerable casualties, many people killed. gordon: the explosive may have been a compound called tacp. --[indiscernible] tatp. this footage shows the devastation when a detonates.

it is also thought to have been used in the manchester arena attack this year. that involve the suicide bomber. but today's attacker wanted to get away. and used a timer. that's similar to damon smith seen here leaving a time device at north greenwich a year ago, which was spotted before when talk. -- before it went off. today, hundreds of counterterrorism detectives have been deployed in this investigation. they've been forensically analyzing this device, looking for fingerprints and dna. they have also been scouring cctv, looking for an individual carrying this bag onto the tube and getting off without it. that will have been the starting point for their manhunt. mi-5 are helping the investigation. they all want to know if the individual was part of a group or acted alone. as often has been the case was really if they were previously known to the authorities. >> unfortunately, it would not be surprising, a concept of a lone wolf now would be accurately described as a known

wolf. attacks have been committed by individuals who were known in some way to the counterterrorism police or mi-5 before hand. gordon: officials here have reacted with irritation to this tweet from donald trump. "another attack in london by a loser terrorist. these are sick and demented people who were in the sights of scotland yard. must be proactive." theresa may responded that it is never helpful to speculate about an investigation. for the fifth time this year, the country is dealing with the aftermath of an attack. with no sign of an arrest, officials felt they had to raise the threat level amid fears the danger has not yet passed. jane: very worrying times in the u.k. now, the united nations is meeting an emergency session

today do to address the issue of north korea's latest missile test. again, the flight path went over japan, creating new tension in the region. it comes on the heels of a nuclear bomb test two weeks ago. rupert wingfield-hayes reports from japan. [sirens] rupert: in northern japan friday began with this very unpleasant wake up call. [speaking japanese over p.a.] speakers blared out warnings. commuters were cleared from railway stations and trains halted. foreign tourists were left bemused by what was going on. far above, a north korean missile was flying past. this behind me here is the sea of japan. we've come up here from tokyo because this is the place most affected. a place where this morning there were woken up by sirens and by that message that a north korean

missile was flying overhead. for the people who live here in towns and cities along the coast, this is the second time that has happened in less than three weeks. this afternoon we found -- him playing with his daughters and fretting about how to protect them. >> i want to protect my kids but we do not have a basement. we have nowhere to hide. only 10 minutes to reach depend. -- to reach japan. what can we do in 10 minutes? reporter: erica told me she is frustrated by japan's refusal to talk to north korea. >> the sirens to scare people. there is nothing we can do. what is the point? the government needs to have a real policy. they need to talk to north korea. rupert: this is the tuype of -- type of missile that is thought to have been fired, and it moved further than any rocket had ever gone before.

in tokyo, prime minister shinzo abe marched out to face the cameras again. >> if it continues down this road, north korea will have a dark future. his words have an increasingly hollow ring. beneath this house, one person has taken matters into his own hands. behind a steel door, he takes me into his own nuclear bunker. >> since these missile launches began, i have had so many calls about the air feel trish's system, i had 800 inquiries this year. >> he's safe in his bunker but the rest of japan is wondering what it can do and when the next missile launch will come.

jane: a brief time ago i spoke with someone at the former state department. that thele have said only thing north korea understands is the threat of force. it has been threatened with force. so why is it continuing to fire missiles? >> well, threats of force are actually different from use of force. it is important to demonstrate our willingness to use it. the problem is is that we have actually had a rather effective deterrent, this sort of balance for the last years since the korean war because both on-site - sides understand we started -- restarting the korean war has devastating consequences. that is the uneasy balance we have lived with. jane: the national security adviser h.r. mcmaster has says there is a military plane, but we know that could cost millions

of lives. at what point, does the threat become reality and a price worth paying? >> well, yes. it's important to understand the military options have always been on the table. so, this controversy or the sort of hype about president trump has put it on the table, every u.s. president has had it on the table since president truman. now, um, we often understand this is very serious problem and it is indeed a threat, but a threat to global security because north korea's continued flagrant violation of treaties, including the npt, really threatens the non-proliferation regime. this is consequences for every country, including the u.k., all the european powers, certainly the united states but also the future of global stability. frankly, it is far more than north korea. jane: i'm sure it will be coming up in the united nations general assembly next week, but what more can the world do? we've had nine rounds of

sanctions. >> 20 some odd u.n. resolutions and every time north korea has committed one of these acts of aggression. the point is, also, that this is really a test of collective security and of the u.n. and if the united nations is unable to take strong action, that includes russia and china, really taking serious actions, instead of passing resolutions, then i think that also unravels our system today. jane: but like north korea dg get a sense that china and russia are going to change their attitude? >> ultimately, no. and the reason is because russia and china essentially share the same strategic goals as north korea. north korea has specific goals, which needs to accomplish through what it believes it needs is nuclear weapons. um, and that is essentially to change this to teach a -- the strategic environment in east asia.

essentially have the u.s. leaves or u.s. influence declines. and that friendly service russia and china's long-term goals. i don't see russia and china prioritizing north korea's nuclear program for something that they essentially all agree on. jane: thank you very much for joining. in the last few minutes north korea's state media is reporting that kim jong-un is saying the final goal is to establish equilibrium of real force with the united states. launchedd belarus have a large-scale joint military exercise. you're watching in fact, "bbc world news america." for 13 years of has been sending home some of the most remarkable image of saturn. missiontoday, cassini came to an end when the page plunged the space probe into the atmosphere. it documented extraordinary discoveries.

russia and belarus have launched a large-scale military exercise. nearby nato -- countries very nervous. it is one of russia's biggest military exercises since it was - -it annexed crimea. here is more. reporter: we have been invited on a surveillance late, traveling with the top nato commander. that russia begins its west military exercises just across the border. latvia, whofrom have already asked for and received nato support. this flight is more assuring. >> 0211533 -- reporter: once the sensors are

switched on, the crew compares the air space with the exercises taken place across belarus and western russia. deputye, too, for nato's supreme commander to see what russia is up to. worry about the lack of trust but anyway, that is going to be -- reporter: there is no sign of that from the russians? >> not at the moment, no. reporter: and that worries you? >> it worries me. reporter: and this is what worries him -- large-scale military maneuvers that take place every four years. in the past they have been used as cover for offensive operations. it's what happened in you came in 2014 -- in ukraine. nato has stepped up their military exercises. but the a line says there is a key difference -- they say all of their actions are transparent and open. >> download complete. reporter: on this flight, they

spot a russian spy plane doing the same as them. even a concern nato thinks that this time the russians are only flexing their muscles, but both sides are keeping a watchful eye on each other. jane: for 13 years it has been sending home some of the most remarkable images of saturn. earlier today, cassini's mission came to an end. during its epic journey cassini gave us new insight into this mysterious planet. david: it has been a journey that sounds like something from science fiction. nasa conjuring up animation of the cassini spacecraft flying around the rings of saturn but this really did happen. and these are some of the images

the mission captured. the planet seen from closer than ever before. the strange detail of its rings. a jet stream in the shape of a hexagon. and an utterly weird collection of moons. today the expedition had to come to an end. >> i'm going to call this the end of mission. reporter: at mission control, hugs and applause. for many, it has been the work of a lifetime. no surprise -- there were mixed feelings as the final signal reached earth. >> it has been a part of my life for 20 years, we spent day in and day out thinking about cassini. focusing on the science. my career has been based on cassini. it is really hard to see that go. reporter: saturn is the most distant world to have been explored for so long, and the cassini spacecraft almost as big

as a bus has achieved something never attempted before. it's given us unprecedented views and have led to dozens of discover spurred the mission is -- the mission is described as one of the most remarkable journeys of exploration. it has been orbiting saturn for 13 years. now, it is one of saturn's moons that's produce the most startling revelation. plumes of vapor were spotted blasting out of it. this turned out to be water. so, let's take a closer look inside what we now know under a covering of ice there is an ocean and scientists have come to an amazing conclusion that in here, there is every ingredient needed for life. this opens up a whole new realm of possibilities in the search for life beyond earth. and the discovery and conditions on these moons is a real breakthrough for the scientists who started her career at nasa three decades ago when the mission began.

>> we wanted to know is there life in their ocean? could there be oceans inside of other moons? it will take future missions to answer those questions. reporter: the mission captured these images of titan. and sound the spacecraft recorded. to make sure cassini did not contaminate any of the worlds where they may be life, it was sent to its discretion -- its destruction. has raised tantalizing new questions. jane: for more on the memorable mission, i spoke with victoria jaggard a senior science editor at national geographic. thanks for coming in. national geographic has a fantastic interactive of the grantor. what is your favorite bit? >> it is a beautiful piece of work. one of our graphic designers put that together for us in association with one of our writers. my favorite part of it is being able to watch they tangle of

orbital motion as cassini moving its way through the saturn system, using thruster and gravity and getting this absolutely grand tour of the entire system, not just the planet but the core. jane: in terms of scientific discovery, what about that? >> well, one of the most important scientific discoveries from cassini is the idea that some of its moons have some of the building blocks of life. the icy moon is this crest of ice around what we believe is a global ocean. that cassini helped us find. the hazy moon titan almost like an alternate universe version of earth. that has an atmosphere, thunderstorms and lakes and rivers. so cold, all of the liquids are hydrocarbons, not water. it's still stuffed with organic materials that we think could be the building blocks for some type of like. -- of life.

jane: that is why cass -- why cassini has pledged to her death to avoid contaminating these environments. is this something scientists have recently become concerned about? >> nasa especially has been concerned about planetary protection since the get-go. even the apollo mission when they came back had to be quarantined. because they were worried about them bringing materials back to earth. they could be harmful. since that time, we worried about the possibility for us contaminating the solar system with microbes if we were let cassini go and continue to float around the system was it was out of juice. there is a chance that we could contaminate any of those moons. and we would be risking our chance of finding life or organic somewhere else in the solar system. jane: fleeting thought. a lot of parents have to bribe their kids to mow their lawn. but frank from falls church, virginia, has a passion for it. he offered to mow the lawn at the white house.

today he got his chance in the that's it from us. have a lovely weekend. and thank you for watching "world news america." >> with the bbc news app, our vertical videos are designed to work around your lifestyle, so you can swipe your way through the news of the day and stay up to date with the latest headlines you can trust. download now from selected app stores. >> funding of this presentation is made possible by the freeman foundation and kovler foundation, pursuing solutions for america's neglected needs. >> planning a vacation escape that is relaxing, inviting, and exciting is a lot easier than you think. you can find it here in aruba. families, couples, and friends can all find their escape on the

island with warm sunny days, cooling trade winds, and the crystal blue caribbean sea. nonstop flights are available from most major airports. more information for your vacation planning is available at aruba.com. >> "bbc world news" was presented by kcet, los angeles.

captioning sponsored by newshour productions, llc >> sreenivasan: good evening. i'm hari sreenivasan. judy woodruff is on assignment. on tonight's pbs newshour: >> i really was not ready or equipped to run for president against a reality tv candidate. >> sreenivasan: one on one with hillary clinton. from north korea to racism, the former presidential candidate tells judy woodruff what she thinks are the greatest threats to the nation. >> in many ways, the trump presidency poses a clear and present danger to the country and to the world. >> sreenivasan: also ahead this friday, the voices of the vietnam war. in the second part of our look at ken burns' and lynn novick's new documentary, how telling the whole story takes all perspectives. >> we as americans always assume we're at the center of this y