Anti-racism groups and other protesters rallied in Paris to support victims of police violence after a young black man was allegedly raped with a police baton earlier this month.
Paris police installed a security perimeter around Saturday's rally on the Place de la Republique in eastern Paris.
Far-right presidential candidate Marine Le Pen, meanwhile, urged the government to ban the protest out of respect for police who are ensuring public safety in France during the country's ongoing state of emergency.
Demonstrators carried banners reading "Justice for Theo," the name of the 22-year-old alleged rape victim, and called for justice in the investigation.
The protesters argue that Theo is just one example of many young men unfairly targeted by police in ID checks and sometimes abused.
Theo, whose last name has not been released, was hospitalised for two weeks after the reported attack in his hometown of Aulnay-sous-Bois north-east of Paris.
One officer has been charged with rape in the case, and three others with aggravated assault. All deny intentional wrongdoing.
After an apparent video of the attack circulated online, angry youth torched cars and clashed with police for several days in suburbs around Paris.
The violence was reminiscent of riots in 2005 that exposed France's long-running problems between youths in public housing projects and police.
