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.
The Islamic State group has said it was behind Friday's gun and bomb attacks on Parisian bars and restaurants, a concert hall and the Stade de France, the country's main sports stadium.
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 with two other men near the Belgian border when it was stopped by police, officials said, but was released after checks.
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.
Police have described Salah Abdeslam as dangerous, and warned people not to approach him.
French news channel BFMTV quoted an investigation source as saying that he and one of the other attackers were known to the Belgian authorities.
He is one of three Belgium-based brothers linked to Friday's attacks, officials say.
Names of the France terror attackers
- Salah Abdeslam, 26 - urgently sought by police
- Mohammed Abdeslam - reportedly arrested in Belgium
- Brahim Abdeslam, 31 - named as attacker who died near Bataclan concert hall
- Omar Ismail Mostefai, 29, from near Paris - died in attack on Bataclan
- Bilal Hadfi, 20 - named as attacker who died at Stade de France
- Four other attackers died during the assaults in the city
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