Video report by ITV News Correspondent Martin Geissler
The Manchester Arena bomber has been confirmed as 22-year-old Salman Abedi by Greater Manchester Police (GMP).
Abedi is believed to have travelled to Syria and had "proven" links with so-called Islamic State, France's interior minister Gerard Collomb said.
The UK Home Secretary Amber Rudd today said that Abedi, of Libyan, descent, had been known to intelligence services "up to a point".
She said that it was probable that he had an accomplice in carrying out the suicide attack.
Abedi, 22, was born in Manchester after his parents fled the regime of dictator Muammar Gaddafi and lived within a tight-knit Libyan community in the city.
Neighbours in Manchester said they remembered an abrasive, tall, skinny young man who was little known in the neighbourhood, but often seen in traditional Islamic clothing.
They said the young man at the property had many visitors, one man dropping by regularly to pick him up in a Toyota Yaris.
Video analysis by ITV News Security Editor Rohit Kachroo
The French interior minister said that both British and French intelligence services had information that Abedi had been in Syria.
"All of a sudden he travelled to Libya and then most likely to Syria, became radicalised and decided to commit this attack," he told French television.
Abedi has also visited Libya many times, returning as recently as this week from his latest trip.
He is thought to have been radicalised in recent months.
British officials have been less forthcoming.
Ms Rudd has said that intelligence services were aware of Abedi but he does not necessarily seem to have been considered a high threat.
She said the attack was "more sophisticated" than some plots and therefore "it seems likely, possible that he wasn't doing this on his own" in an interview with BBC Radio 4's Today programme.
She also added that it was not yet clear whether Islamic State directed the attack.
Abedi was registered as living at Elsmore Road in the city as recently as last year, the location where police earlier raided a red-bricked semi-detached property, ordering nearby residents to remain indoors while they carried out a controlled explosion on the front door.
Abedi is also registered as having lived with his mother Samia Tabbal, father Ramadan Abedi and a brother, Ismail Abedi, who was born in Westminster in 1993.
He is thought to have a younger brother, named as Hashim Abedi, and a sister Jomana, whose Facebook profile suggests she is from Tripoli, the Libyan capital, but lives in Manchester.
Abedi was a student at Salford University where he studied on a business and management course.
A source said he dropped out without completing his degree.
Dr Sam Grogan, the university's Pro-Vice Chancellor Student Experience, said: "All at the University of Salford are shocked and saddened by the events of last night. Our thoughts are with all those involved, their families and their friends."