British police on Tuesday identified the suicide bomber who killed 22 people, including children, in an attack on a crowded concert hall in Manchester, and said they were trying to establish whether he had acted alone or with help from others.
The suspected attacker was named as Salman Abedi, aged 22. Two US officials who have been in contact with British authorities said he was believed to have travelled to Manchester from London by train.
"Our priority, along with the police counter-terrorism network and our security partners, is to continue to establish whether he was acting alone or working as part of a wider network," Manchester Police Chief Constable Ian Hopkins said.
Police raided houses in the northern English city and arrested a 23-year-old man after Monday evening's attack, the deadliest in Britain for 12 years.
Prime Minister Theresa May called it an act of "sickening cowardice" targeting "defenceless children and young people".
What do we know about the attack at Ariana Grande concert?• The worst terrorist incident on UK soil since 2005 comes just two weeks before a general election• British police said 22 people, including children, were killed and 59 people had been treated in hospital• Many of the fans at the concert were young people. The explosion sparked panic as thousands of people rushed for the exits• More than 400 officers were involved in the operation overnight• US singer Ariana Grande had just finished the concert at the Manchester Arena, the largest indoor arena in Europe with capacity for 21,000 people, when the bomber set off his device• Parents hunted for missing children after the blast. Many turned to social media to seek loved ones• Transport police said they believed the attack had taken place just outside the Manchester Arena near a public foyer which linked to the train station• What about the June 8 election? Major British parties have all suspended campaigning• The blast occurred on the anniversary of the murder of soldier Lee Rigby, who was hacked to death on a London street on May 22, 2013
Islamic State, now being driven from territories in Syria and Iraq by Western-backed armed forces, claimed responsibility for what it called a revenge attack against "Crusaders", but there appeared to be contradictions in its account of the operation.
"All acts of terrorism are cowardly," May said in a statement outside her Downing Street office after a meeting with British security and intelligence chiefs.
"But this attack stands out for its appalling sickening cowardice, deliberately targeting innocent, defenceless children and young people who should have been enjoying one of the most memorable nights of their lives."
She said security services were working to see if a wider group was involved in the attack, which fell less than three weeks before a national election. The election campaign has been suspended for now as a mark of respect.
May spoke to US President Donald Trump, French President Emmanuel Macron and several other foreign leaders on Tuesday about the attack, her spokesman said. She also visited the police headquarters and a children's hospital in Manchester.
Desperate parents and friends posted heart-wrenching messages and pictures on social media in the search for their loved ones who had been at the concert by Ariana Grande, a US singer who has a large number of young and teenage fans.
"Please...please retweet. Looking for my daughter and her friend," Michael MacIntyre wrote on Twitter, alongside an image of his daughter Laura and her friend Eilidh.
Police raided a property in the Manchester district of Fallowfield where they carried out a controlled explosion.
Witnesses in another area, Whalley Range, said armed police had surrounded a newly built apartment block on a usually quiet tree-lined street.
Manchester remained on high alert, with additional armed police drafted in. London Mayor Sadiq Khan said more police had been ordered onto the streets of the British capital.
Monday's attack was the deadliest in Britain since four British Muslims killed 52 people in suicide bombings on London's transport system in 2005. But it will have reverberations far beyond British shores.
Attacks in cities including Paris, Nice, Brussels, St Petersburg, Berlin and London have shocked Europeans already anxious over security challenges from mass immigration and pockets of domestic Islamist radicalism. Islamic State has repeatedly called for attacks as retaliation for Western involvement in the conflicts in Syria and Iraq.
Reuters