The man who carried out a suicide attack in Manchester was “likely” to have not acted alone, Home Secretary Amber Rudd says.
Salman Abedi killed 22 and injured 64 when he blew himself up at the Manchester Arena on Monday night.
Police arrested three men in Manchester on Wednesday. Abedi’s 23-year-old brother was arrested on Tuesday.
The official threat level in Britain was raised late on Tuesday for the first time in a decade to its highest level, “critical”, meaning an attack could be imminent.
Interior minister Amber Rudd said up to 3,800 soldiers would be deployed on Britain’s streets, taking on guard duties at places like Buckingham Palace and Downing Street to free up police to focus on patrols and investigatory work.
Police have named British-born Salman Abedi, 22, as the perpetrator of the bombing at the Manchester Arena indoor venue at the end of Monday’s concert by US pop singer Ariana Grande, attended by thousands of children and teenagers.
The identities of Abedi’s victims were becoming known little by little. They included an eight-year-old girl, several teenage girls and a 28-year-old man.
A Polish couple who had come to collect their daughters after the concert also died, Poland’s foreign minister said. The daughters were safe.
“It seems likely, possible, that he (Abedi) wasn’t doing this on his own,” Rudd told BBC radio. She also said Abedi had been known to security services before the bombing.
Prime Minister Theresa May chaired a meeting of the government’s Cobra emergency response committee at her Downing Street office.
Abedi was born in Manchester in 1994 to parents of Libyan origin, according to US sources citing British contacts.
Asked about reports that Abedi had recently returned from Libya, Rudd said she believed that had now been confirmed.
French Interior Minister Gerard Collomb said British investigators had told French authorities Abedi had probably traveled to Syria as well and that he had “proven links” to the Islamic State militant group.
France, which has repeatedly been hit by devastating militant attacks since 2015, extended emergency powers in the wake of the Manchester bombing.
Britain has a national election coming up on June 8 but all campaigning has been suspended since the bombing. Coverage of the attack and its aftermath has pushed out political news from the British media.
It was the deadliest attack in Britain since July 2005, when four British Muslim suicide bombers killed 52 people in coordinated attacks on London’s transport network.
The Manchester bombing also left 64 people wounded, of whom 20 were receiving critical care for highly traumatic injuries to major organs and to limbs, a health official said.