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The UK terror threat level has been raised to its highest level from severe to 'critical' after the Manchester Arena bombing that claimed 22 lives and injured several others, signifying that another attack may be imminent.
British Prime Minister Theresa May, after chairing a meeting of the government's emergency Cobra committee, announced that the country's terror threat level has been raised to its highest level based on evidence gathered during the investigation of the deadly attack at a Manchester Ariana Grande concert.
She said the military personnel will help armed police officers in guarding key sites.
Prime Minister May has also triggered "Operation Temperer", an emergency plan to put thousands of soldiers on the streets in response to a major terrorist threat, local media reports said.
Former Prime Minister Tony Blair had also deployed soldiers in response to a terrorist threat when he had sent tanks and 450 members of the armed forces to guard airports in 2003 after warnings of a plot to bring down an airliner.
Telegraph quoted May as saying that the police had asked for military support and Defence Secretary Sir Michael Fallon has approved the request.
'Critical' threat level means that a terror attack could happen on British soil 'imminently'.
The Guardian quoted Scotland Yard assistant commissioner Mark Rowley as saying that the doubt about whether a wider group was involved in the Manchester attack led to the decision to raise the threat level.
The suicide bomber, who killed 22 people at the deadly Manchester Arena, has been identified as 22-year-old Salman Abedi, Telegraph quoted Manchester Police Chief Constable Ian Hopkins, as saying.
"Priority is to continue to investigate whether he was acting alone or working as part of a wider network," he added.
There were also reports that Islamic State group has claimed responsibility of the attack.
Meanwhile, the Greater Manchester Police have arrested a 23-year-old man in connection with the Manchester Arena bomb attack on Tuesday even as Prime Minister May condemned the "sickening cowardice" of the perpetrator.
The police detained a man in the south of the city after raiding a flat in a newly-built four-storey block of apartments in Carlton Street in Whalley Range in an operation linked with the attack.