Tens of thousands of people marched in France Saturday to protest police violence in demonstrations organised by the left, with clashes breaking out on the margins of the Paris rally.

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

In the capital, demonstrators of all ages held placards proclaiming "Stop state violence", "Don't forgive or forget" or "The law kills".

Demonstrators took particular aim at article 435-1 of the internal security code, introduced in 2017, which extends authorities' leeway to shoot in the event of a suspect's refusal to comply.

They were responding to a call by the radical left including the hard-left France Unbowed (LFI).

Unions said some 80,000 people joined the protests across France, including 15,000 in Paris, but the interior ministry put the number at 31,300 nationwide, with 9,000 in Paris.

- 'Unacceptable violence' -

The government denounced "unacceptable violence" on the margins of the march in Paris, after officers were trapped in their police vehicle when it was attacked, an AFP correspondent said.

Hundreds of hooded people wearing black broke away from the main march of several thousand people in Paris.

They smashed the windows of a bank branch and threw objects at a police car stuck in traffic, an AFP reporter said.

Paris police said the car was attacked with a crowbar and that anti-riot officers were forced to intervene.

Police said three officers were slightly injured.