Britain's international terror threat level was last at the critical level in June 2007. Photograph: (Reuters)
May said members of the armed forces would be positioned at key sites to free up police for patrols and military personnel might be deployed at public events
Britain's armed forces will be deployed to boost security, Prime Minister Theresa May said on Tuesday, as the country raised its terror threat to the highest level of "critical" after a suicide attack in Manchester that killed 22 people, including children.
May said members of the armed forces would be positioned at key sites to free up police for patrols and military personnel might be deployed at public events such as concerts and sports events as a further attack was seen as potentially imminent.
May said the independent body which sets the threat level had recommended it be raised from "severe" after a man named by police as Salman Abedi set off an improvised bomb on Monday night as crowds streamed out of a concert.
"It is now concluded on the basis of today's investigations that the threat level should be increased for the time being from severe to critical," she said in a televised statement after a meeting of the government's crisis response committee.
"This means that their assessment is not only that an attack remains highly likely but that a further attack may be imminent."
Britain's international terror threat level was last at the critical level in June 2007.
May, who is due to contest a national election on June 8, said the man named by police as the attacker, Salman Abedi, was born and brought up in Britain and investigations into whether he was working alone were ongoing.
"The work undertaken throughout the day has revealed that it is a possibility we cannot ignore that there is a wider group of individuals linked to this attack," she said.