France's anti-terror police arrested five people allegedly linked to jihadist groups in morning raid in Lunel, a small southern town that has grown a dubious reputation as a recruitment hotspot for Islamic fundamentalists.
Several roads were under police lockdown as Special Forces officers stormed a number of flats in the town centre, local press reported.
The five suspects held are accused of having ties with French extremists fighting in Iraq and Syria. A police source told Reuters two had recently returned from the conflict there.
Lunel, a town of 26,000 the Herault region near Montpellier has seen about 20 of its inhabitants joining fighting in the Middle East in recent months.
Six of them, aged between 18 and 30, have died in Syria since October, accounting for about 10% of the total number of Frenchmen killed in the war-torn country.
The high number of Islamic radicals compared to its small population has placed Lunel under media and authorities' spotlight, particularly after this month's deadly terror attacks in Paris.
The president of the local Al Baraka mosque, Lahoucine Goumri, draw widespread criticisms in December for claiming that President François Hollande's policies were to blame for the high number of French Muslims joining jihad. Goumri has since been replaced.
The police raid came as France has tightened security in the wake of the attacks that left 20 people, including three Islamist gunmen dead in Paris.