A government minister has raised concerns about a growing number of terrorists "self-radicalising" in the wake of the Liverpool bomb attack.
Home Office minister Damian Hinds said the coronavirus pandemic may have “exacerbated” the number of people radicalising online.
It comes after police named Emad Al Swealmeen as the man who died when a homemade device exploded in the back of a taxi outside Liverpool Women’s Hospital shortly before 11am on Remembrance Sunday.
The 32-year-old was believed to have been an asylum seeker from the Middle East who converted to Christianity in 2017.
The driver of the cab, named locally as David Perry, survived the incident and has since been discharged from hospital.
Four men arrested under terrorism laws in the Kensington area of Liverpool – three aged 21, 26 and 29, who were held on Sunday, and a man aged 20 who was detained on Monday – have been released without charge.
Police said they were treating what happened in Liverpool as a terror incident.
The UK’s terror threat level was raised from “substantial” to “severe” on Monday, meaning an attack is “highly likely”.
The explosion in Liverpool was the second terror incident in a month, after the death of Conservative MP Sir David Amess.
Security minister Damian Hinds said it was a concern the coronavirus lockdown may have increased the number of potential terrorists.
He said: “There’s a long-standing, now, route of what’s called self-radicalisation.
“So, a mixture of consuming propaganda on the internet, and also interacting with other people of perhaps similar mindset on the internet.
“During the coronavirus period and lockdown there have been more people spending more time in front of their computer screens. I mean it’s only a tiny, tiny proportion of those for whom they go down this dark route but, yes, of course this is a concern.
Hinds warned that people must remain “vigilant”, but he said there were “multiple times when we are protected from this, there’ve been over 30 late-stage plot disruptions in the last few years”.
Watch: Couple who sheltered Liverpool terror suspect speak out
Al Swealmeen had at one point lived in Liverpool with Christian volunteers Malcolm and Elizabeth Hitchcott.
Speaking to the Daily Mail, Mr Hitchcott said: "There was nothing to suggest he could go on to become radicalised."
Mrs Hitchcott told ITV: “What a waste of a life. But the one thing I suppose to be thankful for is that he did not kill anyone else.
“It’s so terribly sad. We just loved him. He was a lovely guy and we are so shocked. It’s all too much.”
Mr Hitchcott told ITV: “I mean he lived here for eight months, and we were living cheek by jowl. There was never any suggestion of anything amiss.”
He said Al Swealmeen formally converted from Islam at a ceremony in Liverpool's Anglican Cathedral. The cathedral, which held the city's main Remembrance Day service on Sunday, is not far from Liverpool Women's Hospital.
Mr Hitchcott said Al Swealmeen had been sectioned under the Mental Health Act for about six months following an incident involving a knife.
Mr Hitchcott told The Sun that Al Swealmeen had been claiming asylum in the UK for several years.
He told the newspaper: “The UK asylum people were never convinced he was Syrian and he was refused asylum in 2014.
“He had his case rejected because he has been sectioned due to some mental health incident where he was waving a knife at people from an overpass.
“He was going to put in a fresh asylum claim. Once he had done that, it was possible for him to be housed again by the Home Office and get £35 a week.
“He didn’t want to stay here any more. So he could get the accommodation, I gave him notice to leave.”
Asked about reports Al Swealmeen had an asylum claim rejected, Hinds said he would not comment on an inidividual case.
Shadow home secretary Nick Thomas-Symonds suggested there should be a judge-led inquiry into so-called “lone wolf” attackers.
Police carried out searches on Monday at Rutland Avenue, the address where detectives said Al Swealmeen was picked up by the taxi, and a second address in Sutcliffe Street, where officers believe he previously lived.
Assistant Chief Constable Russ Jackson, from Counter Terrorism Police North West, previously told journalists the explosive device had been “manufactured” and the force’s assumption was that it was built by Al Swealmeen in the taxi.
A motive is still unclear but the incident has been declared a terrorist attack. MI5 is assisting police with the investigation.
In an update on Monday evening, Assistant Chief Constable Jackson said “significant progress” had been made.
“We have a much greater understanding of the component parts of the device, how they were obtained and how the parts are likely to have been assembled,” he said.
“Following interviews with the arrested men, we are satisfied with the accounts they have provided and they have been released from police custody.”
Watch: CCTV shows 'hero' taxi driver escaping Liverpool cab explosion