French police used have tear-gas to disperse stone-throwing youths in the centre of the southeastern city of Lyon.
The clashes erupted at around 4pm in the historic Place Bellecour, where a large number of police were deployed to head off possible disturbances. At least two people were arrested by police.
It was the first time police and rioters have clashed in the heart of a major French city since the rioting began more than two weeks ago.
Heavy police presence in Paris
Thousands of police are patrolling central Paris to enforce a ban on large gatherings likely to provoke disturbances and prevent urban unrest reaching the heart of the capital.
Police said they had monitored calls for violence on internet sites and that potential targets included the Champs Elysees and the Eiffel Tower.
Disturbances intensified last night after appearing to ease over the previous three days.
502 vehicles were set ablaze across France, compared to 463 the previous night and two fire bombs were thrown at a mosque in southern France, damaging the entrance.
Unrest also hit areas including Strasbourg, Marseille, Lyon and Lille.
President Chirac and the French government have been heavily criticised over their handling of the crisis.
The violence, described as the worst in France since May 1968, erupted after the accidental deaths of two youths who were electrocuted in an electrical sub-station where they were hiding from police.
