LONDON — Britain was hit by a terrorist attack on Friday morning, when a crude bomb exploded on a crowded London Underground train, injuring commuters, sowing panic, disrupting service and drawing a heavy response from armed police officers and emergency workers. Hours later, the Islamic State claimed responsibility.
The bomb exploded at 8:20 a.m. on an eastbound District Line train leaving the Parsons Green station in Southwest London.
“This was a detonation of an improvised explosive device,” Assistant Commissioner Mark Rowley of the Metropolitan Police, a top counterterrorism official, said at a news conference. He urged anyone who had seen what happened or had taken photos or videos of the bombing, to come forward.
The authorities immediately beefed up security around the transit system, as hundreds of police officers and detectives combed the scene for clues.
Officials said that 29 people were hospitalized, several apparently injured as panicked commuters fled. None had life-threatening injuries, and hospital officials described the victims as “walking wounded.” By late Friday afternoon, eight of the 29 had been discharged.
“The train was packed, and I was down the other side of the carriage standing up, looking at my phone and then I heard a big boom and felt this heat on my face,” said Natalie Belford, 42, a hairdresser and beautician who was on the train. “I ran for my life, but there was no way out. The doors were full of people and the carriage was too packed to move down.”
The Islamic State, which has asserted responsibility for a number of deadly terrorist attacks that have struck Europe in the past few years, announced it was responsible for the London Underground bombing.
CreditPool photo by BBC Broadcast
The claim, released later Friday via the militant group’s Amaq news agency, said the bombing had been carried out by a “detachment” of disciples — language that suggested more than one assailant had been involved.
Passengers described seeing a wall of fire. One woman with burns was taken away on a stretcher, and several others were cut or bruised as panicked commuters fled the train and the elevated station.
The National Health Service said that 19 people had been taken to three hospitals and that another three had gone on their own.
It was the fifth terrorist attack in Britain this year, following a vehicular and knife attack near Parliament in March, a suicide bombing at a rock concert in Manchester in May, and a van and knife attack around London Bridge and a van attack outside a London mosque, both in June.
Taken together, the terrorist violence has been the deadliest on British soil since July 7, 2005, when suicide bombers set off explosions on three subway cars and a double-decker bus in London, killing 52 people and injuring scores of others.
The new attack immediately revived concerns that militants might be targeting the Underground, commonly known as the Tube — the world’s oldest subway system and one of the busiest.
Prime Minister Theresa May returned to London from her constituency in Maidenhead, west of the capital, and summoned a meeting of the government’s emergency committee, known as Cobra, for the afternoon. Boris Johnson, the foreign secretary, appealed for calm.
The city’s mayor, Sadiq Khan, a face of resolve following the earlier attacks, issued a defiant statement on Facebook.
“Our city utterly condemns the hideous individuals who attempt to use terror to harm us and destroy our way of life,” Mr. Khan wrote. “As London has proven again and again, we will never be intimidated or defeated by terrorism.”
From the United States, President Trump weighed in on Twitter, saying the bombing was the act of a “loser terrorist.” He said that “sick and demented people” had been “in the sights of Scotland Yard,” but he did not elaborate on what he meant.
Loser terrorists must be dealt with in a much tougher manner.The internet is their main recruitment tool which we must cut off & use better!
— Donald J. Trump (@realDonaldTrump) September 15, 2017
The tweet drew an unusual rebuke from Mrs. May, who told the BBC, “I never think it’s helpful for anybody to speculate on what is an ongoing investigation.”
And the London police said in a statement: “Any speculation is extremely unhelpful at this time.”
At Parsons Green, commuters described a frightening vista.
Ms. Belford, the hairdresser, said she was knocked over twice, and showed a reporter her ripped tights and bloodied knee.
“I knew it was a bomb when I saw people with charred hair and burned faces,” Ms. Belford said. “This has got to be terrorism — a bag full of explosive materials don’t just appear on a train by accident.”
Alex Ojeda-Sierra, 13, a pupil at the London Oratory School, was en route to school with a friend when he heard screaming from other carriages.
He had several bruises on his face.
Adam Davis, a 23-year-old student, said he was in the train car where the device exploded.
“I had my headphones on, then I felt a kind of vibration, followed by a wave of heat, and I looked down and the whole carriage was in flames,” he said. “I just got up and ran, but the carriage door was jammed with people. Everyone was screaming and trying to get out, people had blood on them everyone was pushing. It was like a stampede.”
He added: “I didn’t see any suspicious-looking people, or the bucket that’s on the media. I just saw flames and you think the worst. You think bomb. Terrorism.”
Felicity and Tom Reid said they were on their way to a funeral when the explosion went off on their train.
“We had planned to get a cab, but the traffic was so bad at that time we were worried we would be late,” Mrs. Reid said. “We weren’t in the carriage with the explosion, but we heard the bang and heard people screaming so we started running.”
She added: “You think of the worst: bombs, terrorists, shootings, stabbings. You think worse will follow and you just run for your life. We got lucky, but this is terrifying and a reminder it can happen anywhere. Nowhere is safe.”