A huge manhunt is under way for surviving members and accomplices of the Islamist group that killed 129 people in Paris on Friday night.
Police have named Salah Abdeslam, 26, as a key suspect. He was reportedly stopped by officers in the wake of the attacks – but then let go.
Meanwhile, French aircraft have attacked the Syrian stronghold of IS.
Latest reports from France say police investigating the assaults have carried out a raid in a Paris suburb, Bobigny.
French media organisations say major police operations have also taken place in Jeumont, close to the French border with Belgium, and in the southern city of Grenoble – but it is unclear if they are linked to the Paris attacks.
Seven attackers died in the assault on the French capital, most of them after detonating suicide belts.
Salah Abdeslam, the man named by police as a key suspect, is said to have rented a VW Polo car that was found near the Bataclan concert hall, where 89 people died, and believed to have been used by attackers.
On Saturday he was in a vehicle near the Belgian border which was stopped by police, officials said. He was reportedly questioned, had his papers checked and was then released along with two other men who were also in the car.
It is unclear whether the French authorities had matched the VW Polo found at the Bataclan venue to him at the time he was stopped.
