French police have arrested six people who are suspected of belonging to a radical Islamist cell and of preparing attacks in France, a police source said.

The suspects, aged 22 to 38, were arrested in and near the Paris region last night. They were all known to police for various offences and one had appeared in an anti-terrorism investigation.

They can be held for questioning for up to 96 hours before judges decide whether to put them under formal investigation.

France has been on heightened security alert since January, when its military intervened in Mali to help repel al Qaeda-linked Islamist rebels who had seized control of the north of the former French colony.

A Muslim convert suspected of stabbing a French soldier in a religiously motivated attack was placed under formal investigation last month.

Alexandre Dhaussy, 22, is suspected of stabbing the soldier in the neck while he was patrolling a Paris business district, and then fleeing the scene. The soldier survived and is out of hospital.