Tensions erupted in Paris on Saturday at a protest led by the hard left against police violence, with a police car pelted with projectiles and a bank attacked.

The nationwide protest came just under three months after the point-blank killing by a policeman of a youth outside Paris at a traffic check sparked over a week of rioting in Paris and elsewhere.

Hundreds of people wearing black and in hoods broke away from the main march gathering several thousand people in Paris

They smashed the windows of a bank branch and threw objects at a police car that was stuck in traffic.

Paris police said that the police car was attacked with a crowbar and only the intervention of an anti-riot police unit allowed the release of the vehicle.

Some 30,000 people were expected to protest across France, responding to a call by the radical left including the hard-left France Unbowed (LFI) party. (AFP)