Protesters in France threw firebombs at police who responded with tear gas as hundreds marched against far-right National Front leader and presidential candidate Marine Le Pen.

The skirmishes happened during Sunday's march from suburban Aubervilliers to Paris, near where Le Pen is due to hold a rally on Monday.

The protesters said basic freedoms would vanish if Le Pen, who is one of the top contenders in the first-round presidential vote on April 23, won the presidency.

Her anti-immigration party "is fighting our essential freedoms, our rights, no matter if we are French or immigrant," said Fernanda Marrucchelli.

Anti-racism activist Omar Slauti said the fight against Le Pen should be in the streets, not the ballot box, and denounced the "extreme-right populism" that has spread around Europe.

A presidential run-off is being held on May 7.

AP