He told BFMTV that British intelligence services had informed their French counterparts that 22-year-old Salman Abedi, who was of Libyan origin, "grew up in Britain and then suddenly, after a trip to Libya and then likely to Syria, became radicalised and decided to carry out this attack".
Collomb said it was "possible" that Abedi had had assistance from other people, adding: "In any case, the links with Daesh are proven."
Daesh is another term for the Islamic State jihadist group, which has claimed responsibility for the attack on the concert by US pop star Ariana Grande in which many of the victims were children.
Collomb went further than the revelations to date from British authorities.
British interior minister Amber Rudd told BBC radio today it was "likely, possible" that the bomber "wasn't doing this on his own".
In the wake of the attack, Britain has raised its terror alert level to maximum for fear of an imminent new terror strike.
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