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 on Friday 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.

"We've gone back to an almost normal situation in Ile de France (greater Paris region)," national police service chief Michel Gaudin told reporters.

But warning of violence in the capital, he said: "One can easily imagine the places where we must be very vigilant."

The Paris ban on large gatherings went into force at 10 a.m. (0900 GMT) and was due to run until 8 a.m. (0700 GMT) on Sunday. The heart of the city has largely escaped the violence that has rocked impoverished neighborhoods just outside the city.

Three thousand extra police were brought into the capital on Friday, 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.

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