UK raises its terror alert level to ‘critical’; ISIS claims responsibility for attack

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LONDON — British officials have raised the country's terrorism threat level to "critical' — meaning another attack is expected shortly.

Prime Minister Theresa May acted on the recommendation of the Joint Terrorism Analysis Center after the subway train bombing attack Friday at the Parsons Green station in southwest London. The analysis includes security services, police and government agencies.

The threat was raised from "severe" to "critical" — its highest possible level.

The Islamic State group is claiming that the London subway explosion was carried out by an affiliated unit.

The claim was posted Friday on channels affiliated with the extremist group.

A manhunt is under way after the improvised explosive device was detonated on a crowded subway car, injuring at least 29 people.

May said military troops would augment the police presence in a "proportionate and sensible step."

Passengers reported seeing people with burns to their faces and bodies after the fire on a Tube train at Parsons Green station.

Passengers reported an explosion in a carriage of the train shortly after 8 a.m., during the morning rush hour. Several people appeared to have burn injuries.

The incident happened during rush hour when the Underground system is crowded. Passengers were advised to use alternate routes.

It has sparked a huge manhunt for the perpetrators of what police said was the fourth terrorist attack in the British capital this year.

NYPD Commissioner O'Neill responded to the reports tweeting, "#NYPD closely monitoring incident on London subway moments ago. No direct threates to #NYC, but always remain vigilant/aware of surroundings."