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.
A homemade explosive set off a small fire on a train at a London subway station