Dozens of French police officers have been injured, five critically, in a second night of rioting by youths in a northern suburb of the capital, Paris.
Police said the officers were hurt by stones, fireworks and petrol bombs in Villiers-le-Bel, where many families of North African origin live. Cars and buildings were also set on fire.
Riot police responded by firing tear gas and rubber bullets to keep at bay youths who were attacking them.
The French Interior Minister, Michele Alliot-Marie, has said she believes the violence has been organised.
Youths told reporters they were avenging the deaths of two teenagers on Sunday, whose motorcycle collided with a police car.
Police say the motorbike hit the side of a patrol vehicle, but youths say the car's stoved-in bonnet suggests it rammed the boys, who were not wearing helmets.
Police have denied rumours that the officers abandoned the bodies when they realised the teenagers were dead. Prosecutors have opened an inquiry.
The French President, Nicolas Sarkozy, who is currently on an official visit to China, has appealed for calm.