The terror threat level in the U.K. has been raised from ‘severe’ to ‘critical’, Prime Minister Theresa May said late Tuesday.
The announcement came a day after a deadly suicide bomb attack targeted a concert venue in Manchester where American pop star Ariana Grande was performing Monday night.
“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,” May said.
The terror threat level was raised to critical twice in 2006 and 2007, and lasted a few days.
May confirmed a suspected 22-year-old male suicide bomber was behind the attack that killed 22 victims and injured 59 others in the explosion in the foyer area of the Manchester Arena at the end of the concert that was attended by thousands of children and teens.
The possibility exists others are linked to the suspect and the threat level should be increased to critical, according to the prime minister.
“As Greater Manchester Police confirmed earlier today, the perpetrator was Salman Ramadan Abedi, who was born and brought up in Britain and as the emergency services confirmed throughout the day, his victims were innocent children, young people and their families - our thoughts and prayers are with them all,” she said.
The armed forces will secure key areas instead of police, under Operation Temperer, May said, and thousands of military personnel are expected to take part in security operations across the country.
The U.K.’s most senior anti-terror officer urged calm as authorities investigate the attack. “At this stage it is still not possible to be certain if there was a wider group involved in the attack,” assistant police commissioner Mark Rowley said in a statement.
“At this time we are asking the public to remain calm but alert,” he said. “Look out for anything that seems out of place, unusual or doesn’t seem to fit in with day-to-day life. It may be nothing but if you see or hear anything that could be terrorist related trust your instinct no matter how small.”
May will chair another meeting Wednesday of the government’s emergency Cobra committee, the government said.