Islamic State claims London subway terror attack carried out by affiliated unit

Kim Hjelmgaard | USA TODAY

Show Caption Hide Caption Raw: London blast a terrorist incident Police in London declared the reported explosion on a London subway train a 'terrorist incident.' It's unclear if an actual explosion injured anyone, but at least one witness says some people may have been trampled. (Sept. 15)

LONDON — A homemade explosive set off a small fire on a train at a London subway station during rush hour Friday, injuring 29 people and prompting authorities to raise Britain’s terrorism threat level to “critical,” meaning another attack may be imminent.

The incident, which the Islamic State claimed was carried out by an affiliated unit, happened shortly after 8 a.m. local time when London's Underground system is crowded with commuters and children going to school. Most of the injuries were flash burns, London's Metropolitan Police said.

It was Britain's fifth terrorist attack this year.

Prime Minister Theresa May, acting on the recommendation of the Joint Terrorism Analysis Center, raised the country’s threat level from “severe” to “critical” — its highest possible level. May said military troops would augment the police presence in a “proportionate and sensible step,” the Associated Press reports.

Hundreds of investigators and intelligence officers are hunting for a suspect.

Social media users quickly circulated an image that appeared to show a small bag or bucket on fire inside a train at the Parsons Green station in west London. The image does not show much damage to the train, but eyewitnesses described scenes of panic and chaos as passengers fled the area. Some were injured in the stampede.

"To the man (who) pulled me out of the pile of people on the stairs during the stampede at Parsons Green — thank you," Katherine Manson said on Twitter.

Sophie Raworth, a BBC News presenter at the scene, said she saw a woman lying on a stretcher with burns to her face and legs, according to the broadcaster. Other passengers said they saw a wall of fire flood through the train.

Chris Wildish, who was on the subway train where the fire occurred, told British TV that he saw "a massive flash of flames" that reached up to the ceiling of the train and then the air was filled with the smell of chemicals. He said many of the passengers were schoolchildren, who were knocked around by people trying to get away from the fire.

The Underground's District Line was suspended due to the security alert and the London Ambulance Service sent a hazard team to the area. Police said they would provide more details about the incident once they were confirmed.

London has been repeatedly struck by extremist attacks this year including vehicle attacks near Parliament, on London Bridge and near a mosque in Finsbury Park. Britain's terrorist attack level stands at severe, meaning attacks are highly likely.

More: Britain confronts fifth terror attack this year

More: Trump Twitter barrage calls terrorists 'losers,' touts progress against ISIS

Still, Friday's incident was a potentially lucky escape. Police said the improvised explosive device only partially detonated, likely limiting injuries and saving lives.

"My thoughts are with those injured at Parsons Green and emergency services who are responding bravely to this terrorist incident," May said.

Work colleague was on district line train at Parsons Green when bag exploded #london pic.twitter.com/1yXOsFVAJ1 — Andy Webb (@andyjohnw) September 15, 2017

In a briefing, the Metropolitan Police did not release any information about suspects. Assistant Commissioner Mark Rowley said "Londoners should expect to see an enhanced police presence across the transport system."

President Trump quickly suggested the attack may have been preventable.

"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!" he tweeted.

It was not clear what Trump's assessment of the situation was based on.

"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!" he added.

Asked about Trump's comments, May said: "I never think it’s helpful for anybody to speculate on what is an ongoing investigation."

Otso Iho, an analyst at Jane’s Terrorism and Insurgency Center at consultancy IHS Markit, cautioned that failed or disrupted attacks can act as catalysts for future attacks.

"A failed plot which draws the attention of law enforcement to an existing network can accelerate pre-existing plots," Iho said, citing last month's vehicle and knife attacks in Spain that investigators think were brought forward by the accidental discovery of a bomb-making facility near Barcelona.

More: Why Europe has a greater terror problem than the United States