Home Secretary Amber Rudd said the bomber, identified as British-born Libyan Salman Abedi, "likely" did not act alone when he killed 22 people and wounded dozens at an Ariana Grande concert on Monday night in Manchester.
Officials say soldiers will be deployed to places like Buckingham Palace, 10 Downing Street and Parliament.
U.S. Director of National Intelligence Daniel Coats said Tuesday that despite the group's statement, "We have not verified yet the connection", and noted in a Senate hearing that "they claim responsibility for virtually every attack". May addressed the country Tuesday, one day after a suicide bomber blew himself up at a Manchester concert hall, killing 22 and wounding more than 50. British election rolls listed him as living at a modest red brick semi-detached house in a mixed suburb of Manchester where police performed a controlled explosion yesterday.
Police say shopping centre arrest not connected to Manchester attack
Abedi was born in Manchester in 1994 to parents of Libyan origin, according to US sources citing British contacts. This the third time that Britain had raised the threat level to critical.
A man who murdered children.
The 23-year-old told The New Paper she heard sirens throughout the night, but found out about the blast only an hour after it happened. "To be safe, I think I will not go out for three days".
"Rudd said she wouldn't "go that far" to say the leaks had compromised the investigation".
Flynn may have lied in security review, Democrat lawmaker says
Elijah Cummings (D., Md.), the ranking member of the House Oversight and Government Reform Committee, the New York Times reports . The two Flynn businesses that will be issued subpoenas, according to Warner, were Flynn Intel , LLC and Flynn Intel, Inc.
May met with her top security officials after the Manchester attack and said afterward that, "It is a possibility we can not ignore that there is a wider group of individuals linked to this attack", according to The New York Times.
Sixty-four people are still hospitalised, Jon Rouse of the Greater Manchester Health and Social Care Partnership said Wednesday.
Backup dancer Devyck Bull took to Twitter to denounce those responsible, labelling them "pussies".
United Kingdom to deploy troops after attack, risk now 'critical', says Theresa May
President Donald Trump reacted to the bombing while on a trip in the Middle East, calling those behind it " evil losers ". In London , people gathered at the Trafalgar Square and held flags while observing a minute of silence for the victims.