France's interior minister said Sunday security forces would remain in place "as long as necessary" after a second night of violence in the Paris suburbs sparked when police stopped a woman for wearing a veil.
Manuel Valls told French radio he would keep in place "a significant police presence until a lasting calm is restored" in and around the satellite town of Trappes, south-west of Paris.
Police made four arrests in the region in the early hours of Sunday as they came under a hail of projectiles and rioters burned some 20 vehicles in Trappes and surrounding areas.
Things were calmer than on the previous night, however, when some 250 youths gathered in Trappes and hurled stones at police who responded with tear gas.
A 14-year-old boy suffered a serious eye injury in the clashes and several police officers were also hurt.
The unrest was sparked by an incident on Thursday when an officer stopped a woman wearing a veil.
During this inspection, the woman's husband attacked and apparently tried to strangle the officer, said prosecutors.
However, Muslim groups accused the police of "provocation".
Valls said he did not doubt "for an instant" that the police officers acted with respect towards the woman when conducting their check.
Since April 2011, France has had a ban against full facial veils, outraging many in its Muslim community.
Violations are punishable by a fine of up to 150 euros ($200) or mandatory citizenship training.
Authorities say about 300 women were caught breaking the veil law in the first year it was in force.
A similar outbreak of unrest occurred last month when authorities stopped a 25-year-old woman in Argenteuil, a suburb north-west of Paris, who was wearing a full-face veil, or niqab.
An angry crowd gathered and police fired tear gas and rubber bullets to disperse them.