"We have to find out where they came from... and how they were financed," Francois Molins told reporters.
He said seven attackers had been killed, and that all had been heavily armed and wearing explosive belts.
Friday's attacks, claimed by Islamic State militants, hit a concert hall, a major stadium, restaurants and bars.
Prime Minister Manuel Valls has said France will continue with air strikes against IS in Syria and described the group as a very well-organised enemy.
Mr Molins confirmed that one of the dead attackers had been identified as a 29-year-old Frenchman who had a criminal record, but had never spent time in jail.Omar Ismaïl Mostefai was identified after his finger was found at the Bataclan concert hall and matched fingerprints the police had on file, AFP reported.
