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 Brussels-born 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.
Police searches of suspected Islamists were carried out across France, PM Manuel Valls confirmed.
Earlier French media said a police operation connected to the attacks had taken place in the Paris suburb of Bobigny.
Raids also took place in Jeumont, close to the French border with Belgium, and in the southern cities of Grenoble and Toulouse but it was not clear if they were linked to the Paris attacks. READ MORE OF THIS ON STORY BBC NEWS