MANCHESTER, England (CBSNewYork) -- Prime Minister Theresa May announced late Tuesday that the terror threat level in the U.K. has been raised to "critical" after attack at an Ariana Grande concert in Mancheseter that killed 22 people and injured dozens more.
May said at the recommendation of the Joint Terrorism Analysis Centre, the threat level for the U.K. has been increased for the time being from severe to critical. She said this means not only that an attack is still highly likely, but that a further attack may be "imminent."
At a news conference late Tuesday, May said in reaction to increased terror alert level, armed military personnel will be deployed to supplement police forces. The military personnel will replace police at some major events.
May said the increased deployment was a necessary and proximate response to the attack and the threat level, and noted that terrorism has been a threat in the U.K. for many years.
"I do not want the public to feel unduly alarmed," May said.
May added: "We stand defiant. The spirit of Manchester and the spirit of Britain is far mightier than the sick threats of depraved terrorists. That is why terrorists will never win, and we will prevail."
Meanwhile, police have confirmed the identity of the man who they believe was behind the attack.
"I can confirm that the man suspected of carrying out last night's atrocity is 22-year-old Salman Abedi," Manchester Police Chief Ian Hopkins said Tuesday. "However, he has not yet been formally named by the coroner and I would not wish to comment further about him."
CBS News sources confirmed that Abedi was known to British authorities. Hopkins said the priority of investigators is now " to establish whether he was acting alone or working as part of a larger network."
The Islamic State group claimed responsibility for the bombing, but Director of National Intelligence Dan Coats said the U.S. has not verified that information.
"ISIS has claimed responsibility for the attack in Manchester," Coats told lawmakers Tuesday while testifying before the Senate Armed Services Committee. "Although they claim responsibly for virtually every attack, we have not verified yet the connection."
ISIS said Tuesday that one of its members carried out the attack, but the statement did not identify the bomber and some of the facts about the incident appeared wrong, CBS News reported.
It said "a soldier of the caliphate planted bombs in the middle of Crusaders gatherings.'' Officials have said there was only one explosion and there was no indication that other devices were found at or near the arena, according to CBS News.
The group also said the "30 Crusaders were killed and 70 others were wounded,'' which are different numbers than what authorities in Manchester have confirmed. Police have said 22 people were killed and 59 others were hurt.
As CBS2's Jessica Layton reported, Manchester police raided the suicide bomber's home Tuesday, blowing down his front door before entering.
Police said a 23-year-old man has also been arrested in connection with the attack, but released few details, saying only that he was in South Manchester.
The blast happened around 10:30 p.m. Monday local time just after Grande had wrapped up her sold-out concert in the venue with more than 20,000 people in attendance, many of them young girls.
The explosion rocked the concert hall as fans were exiting the Manchester Arena, sending thousands of frightened people running for cover.
"As soon as I heard the bang, I just decided to run," said concertgoer Abigail Lunt. "I didn't know what to do."
Law enforcement officials tell CBS News that the apparent suicide bomber took a train to nearby Victoria station. Police believe the bomber entered the arena through a subway station, detonating the bomb near the ticket area just as people were leaving the concert.
Investigators say that the bomb contained nails and that ball bearings have been recovered, CBS2's Janelle Burrell reported. Police say the attacker was among those whose bodies was found at the arena and said they believe the attack "was conducted by one man."
Authorities said Tuesday that among those killed was an 8-year-old girl, Saffie Roussos. Also killed was a teenage student, Georgina Callander, CBS News reported. Of the 59 injured, medical officials said 12 were children under the age of 16.
"This has been the most horrific incident we have ever faced here in greater Manchester, one that we all hoped we would never see," said Hopkins. "Families and many young people were out to enjoy a concert at the Manchester Arena and very sadly lost their lives."
Queen Elizabeth II issued a statement Tuesday expressing her admiration for the way the people of Manchester reacted to the "act of barbarity."
President Donald Trump also spoke about the explosion Tuesday morning from the West Bank, where he was delivering a joint statement with Palestinian Authority President Mahmoud Abbas.
"So many young, beautiful, innocent people living and enjoying their lives murdered by evil losers," the president said. "The terrorists and extremists and those who give them aid and comfort must be driven out from our society forever.''
The president also called those responsible "losers" and called on "all civilized nations" to help "obliterate this evil ideology."
White House spokesman Sean Spicer tweeted Tuesday that Trump spoke with May "to offer condolences and support on behalf of the US.''
Grande, who was not injured, tweeted: "broken. from the bottom of my heart, i am so so sorry. i don't have words."
Police are now combing through surveillance video, trying to trace the attacker's steps.
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