Thousands of French police patrolled central Paris today to enforce a ban on large gatherings and prevent urban unrest reaching the heart of the capital, including targets such as the Eiffel Tower.
Police said they had monitored calls for violence on Internet sites and that potential targets included the Champs Elysees and the Eiffel Tower.
In a sign of concern after violence rose slightly on the 16th night of clashes, regional authorities for the first time declared a curfew for minors in France's second city of Lyon for Saturday and Sunday night.
Rioting by youngsters angered by unemployment, racism and lack of opportunities has generally dropped in intensity since President Jacques Chirac's government announced emergency measures on Tuesday including curfews. But the number of cars set ablaze by rioters rose slightly again last night, and two fire bombs were thrown at a mosque in southern France, damaging the entrance.
Some 502 vehicles were set ablaze across France, compared to 463 the previous night, and unrest hit areas including Strasbourg, Marseille, Lyon and Lille. But there were fewer incidents of violence in the Paris suburbs, police said.
The Paris ban on large gatherings went into force this morning and is due to run until 8am tomorrow.
The heart of the city has largely escaped the violence that has rocked impoverished neighbourhoods just outside the city. Three thousand extra police were brought into the capital yesterday, the Armistice holiday marking the end of World War One, and riot police have been patrolling key areas, important buildings and suburban trains since then.
Police detained 206 people during the night, during which teenagerss attacked a primary school in Savigny-Le-Temple southeast of Paris and destroyed its creche. Two shops were destroyed in Rambouillet, southwest of Paris, and a person on a scooter threw two fire bombs at a mosque and in the southern town of Carpentras before fleeing.
There was no major damage and no one was hurt but Mr Chirac, prime minister Dominique de Villepin and the French Council of the Muslim Faith (CFSM) swiftly condemned the attack.