MANCHESTER — Prime Minister Theresa May of Britain said Tuesday night (May 23) that the government had raised its terrorism threat level to critical — the highest level — meaning that another attack may be imminent even as the country mourned the victims of the Manchester bombing.

It was only the third time that Britain had raised the threat level to critical.

After a meeting of her top security officials to consider intelligence after the attack in Manchester on Monday night that killed 22 people and wounded dozens more at a pop concert, Ms May said that “it is a possibility we cannot ignore that there is a wider group of individuals linked to this attack”.

She added that soldiers would be deployed to assist armed police, and free some of them up to pursue the possibility that the bomber in Manchester, Salman Abedi, 22, did not act alone and was part of a larger cell that could be planning further attacks.

“This morning, I said that the Joint Terrorism Analysis Centre — the independent organisation responsible for setting the threat level on the basis of the intelligence available — was keeping the threat level under constant review,” Ms May said in a statement.

“It has now concluded, on the basis of today’s investigations, that the threat level should be increased, for the time being, from severe to critical. This means that their assessment is not only that an attack remains highly likely, but that a further attack may be imminent,” the statement said.

The government’s actions Tuesday night came hours after Abedi was identified by police as the bomber who carried out Monday night’s assault, Britain’s deadliest terrorist attack since 2005, an explosion that killed 22 people and injured 59 others at Manchester Arena.

Abedi, whose parents had emigrated from Libya and who lived in a house just 5.5km from the arena, where he detonated a homemade bomb in a public concourse around 10.30pm Monday as a concert by American pop star Ariana Grande was ending and as crowds of teenagers had begun to leave, many for an adjacent train station. Abedi died in the attack.

According to neighbours, Abedi lived with his family in a house in Elsmore Road, in the Fallowfield district. The police raided the house Tuesday afternoon, after setting off a controlled explosion to gain entry. NEW YORK TIMES