French police arrested 20 suspected Islamists in dawn raids, most of them in the southern city of Toulouse where a gunman was shot dead by police last week after going on a killing spree.
Some of the arrests were also carried out in the western city of Nantes.
France's DCRI domestic intelligence agency carried out most of the arrests, with the national police's elite RAID unit providing support in some cases.
The arrests came a day after the burial of Mohamed Merah, who was shot dead by a police sniper on 22 March at the end of a 32-hour siege at his flat in Toulouse.
The 23-year-old had shot dead three soldiers, and three children and a teacher at a Jewish school in a killing spree that shocked the country.
French authorities have charged Merah's brother Abdelkader with complicity in the attacks and said they were looking for other accomplices.
