As Great Britain's terror threat was raised to its highest level for the first time in a decade, counterterrorism officers feared that the person who constructed the "sophisticated" explosive device could be on the loose.
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.
Yesterday York College student Alex Klis said she was looking for her parents Angelika and Marcin, who had been missing since the attack.
He said the priority for detectives was to establish whether Abedi was acting alone or working as part of a wider network when he set off his device after the concert by United States singer Ariana Grande, killing 22 people.More news: Terry 'could not care less' about criticism of staged farewell
Islamic State of Iraq and the Levant (ISIL) claimed responsibility on its social media channels, saying "one of the caliphate's soldiers placed bombs among the crowds".
Witnesses described the horror when the bomber blew himself up outside one of the exits as the mostly youthful audience was leaving, with many parents waiting outside to collect their children.
Martin Reardon, a security analyst and former Federal Bureau of Investigation agent, said that as ISIL loses ground in the Middle East, fighters are likely to stage more attacks in Europe.The bombing also came in the lead-up to a June 8 general election in the UK. She too, was a victim of the senseless terrorism. All parties have suspended campaigning indefinitely, with no activities planned for Wednesday.
US President Donald Trump and European leaders issued vows of defiance.
Some concert-goers said security had been haphazard before the show, with some people being searched and others not. The explosion occurred at the end of a concert, and a suicide bomber was believed to be behind the attack.More news: Markets lack drivers as investors await Fed minutes — FX Focus
Taxi driver Safi Ismail said, "There were so many people coming out and the thing that was getting me was the age - young".
That attack was also claimed by IS, as was one in March by a knifeman at the gates of the British parliament - although police downplayed that claim.
Now, in a dramatic late-night statement inside 10 Downing Street after the Manchester bomb attack, Theresa May has both declared war on terror and changed the rules of the game.
In a city famed globally for its football teams and pop bands like Oasis, The Stone Roses, The Smiths and Take That, showbusiness stars and teams expressed their horror at the carnage.
A support centre for people caught up in the attack was set up at the Etihad Stadium, the home of their rivals Manchester City.More news: Indycar drivers Scott Dixon and Dario Franchitti robbed at gunpoint
Manchester, Britain's third biggest city, was hit in 1996 by a massive auto bomb planted at a shopping centre by the Irish Republican Army (IRA) that wounded more than 200 people.
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