French police investigating the gunman, Mohammed Merah, have arrested at least 20 suspected Islamists, mainly in the south western city of Toulouse.
Merah killed seven people in three separate attacks before being shot dead after a 32-hour siege last week.
The BBC reports the dawn raids were carried out by the domestic intelligence agency, the DCRI, with the support of an elite police commando group known as Raid.
While most of the arrests were in Toulouse, others were in Lyon, Marseille, Paris, Nice and Le Mans.
Earlier, Merah was buried at the Cornebarrieu cemetery in Toulouse.
The mayor of Toulouse had said he did not want him buried in the city, but he was overruled by the President, Nicolas Sarkozy.
About 20 close family and friends of the dead gunman were brought to the site in a secure mini-bus.
The BBC reports that the burial took place under very high security with most of those present police and security personnel.
Gendarmes checked the identity of everyone entering the area and helicopters flew overhead.