 Media playback is unsupported on your device Media caption Footage shows a burning bag on board the Tube carriage at Parsons Green station 
 
 An "improvised explosive device" was detonated on a Tube train in south-west London during Friday's morning rush hour, injuring 29 people. Image copyright PA Image caption One commuter took a picture of the device, which appeared to have wires protruding from a white canister 
 
 Pictures taken of the train show a white bucket on fire inside a supermarket bag, with wires trailing on to the carriage floor. Media playback is unsupported on your device Media caption BBC presenter Sophie Raworth was near Parsons Green station minutes after the incident happened 
 
 At Parsons Green 
 
 Image copyright Reuters Image caption Witnesses have described seeing at least one passenger with facial injuries 
 
 By Jennifer Scott, BBC News 
 
 London has again fallen victim to a terror attack, targeting commuters on their way to work and visitors venturing out into the city. In a televised statement on Friday night, the prime minister said the UK terror threat level was being raised to its highest rating and that armed police and members of the military would be seen on the streets in the coming days. Speaking in Downing Street after chairing a meeting of the Cobra emergency committee, she said there would be an increased armed police presence on the transport network in London. This is a proportionate and sensible step which will provide extra reassurance and protection while the investigation progresses.” 
 
 The prime minister condemned Friday’s bombing as cowardly and the home secretary, Amber Rudd, denounced it as “callous and indiscriminate”. The London mayor, Sadiq Khan, described the attack as hideous and added: “We will never be defeated.” 
 
 The security minister Ben Wallace told the BBC on Saturday: “We haven’t been able at the moment to catch the bomber. The bomber is still out there – or bombers – and we have to get to the bottom of that and follow up the leads.” 
 
 The Met assistant commissioner Mark Rowley, the UK’s most senior anti-terror police officer, said police were “chasing down suspects”. A former army bomb disposal officer said it appeared the initiating charge of the device had exploded but had failed to detonate the main charge. May also criticised the US president, saying: “I never think it is helpful for anybody to speculate on what is an ongoing investigation.” 
 
 Donald J. Trump (@realDonaldTrump) Another attack in London by a loser terrorist.These are sick and demented people who were in the sights of Scotland Yard. Read more 
 
 Image copyright Getty Images Image caption There have been a "number of people" injured, police said 
 
 Media playback is unsupported on your device Media caption Witnesses describe the explosion at Parsons Green 
 
 Emma Stevie, 27, who was on the train when the explosion happened, said she was caught in a "human stampede" and crush on the station steps as people rushed away from the train. There were a lot of people just stamping on each other and I saw someone jumping over [them]. "There was a pregnant woman underneath me, and I was trying really hard not to crush her. St Thomas' Hospital in London said it had treated eight patients but they had now been discharged. pic.twitter.com/zRvRPWOuzA 
 
 Rowley said hundreds of detectives had been drafted in to the investigation, and he appealed to the public for information.
– An explosion and fire on a London Underground train caused panic and injuries during rush hour Friday morning. Police, ambulances, and firefighters were called to the Parsons Green station in the southwest of the city after the blast, which authorities are now calling a terrorist attack, the Guardian reports. Photos and video shared on social media showed a fire in a bucket but no extensive damage to the subway car. Passenger Richard Aylmer-Hall says he saw several people injured in a stampede to escape the packed train. "Suddenly there was panic, lots of people shouting, screaming, lots of screaming," he says. Passenger Peter Crowley tells the BBC that he was sitting on the train when he felt a "really hot intense fireball above my head." He adds: "There were people a lot worse than me." Other witnesses say they saw at least one person being taken away with burn injuries. The London Ambulance Service says at least 18 people were hospitalized after the attack, none of them with life-threatening injuries, the AP reports. London Mayor Sadiq Khan urged Londoners to remain vigilant and said the city "utterly condemns the hideous individuals who attempt to use terror to harm us and destroy our way of life."