French police arrested 70 people at a banned pro-Palestinian protest in central Paris on Saturday that degenerated into clashes between demonstrators and armor-clad riot squads.

The rally had drawn 4,000 people to the capital's Place de la Republique, the Interior Ministry said, while organizers put the turnout at 10,000.

Police who stepped in to disperse the rally responded with tear gas when they were targeted with rocks and other projectiles. About 12 police officers were slightly injured.

Interior Minister Bernard Cazeneuve said that while the young people protesting had been mostly peaceful "there were troublemakers at this demonstration", some of whom had come armed with the intention to cause violence.

"There were 70 arrests and 30 (of them) have been detained, some of whom had significant weapons, including clubs ... and brass knuckles," he said.

The demonstration against Israel's Gaza offensive, which has killed more than 1,000 Palestinians, came after other protests last weekend in Paris and a suburb that had also initially been banned descended into chaos.

Organizers of Saturday's protest had tried going to court to get the ban overturned, but they were unsuccessful, and Cazeneuve had warned that they would be held "responsible for any unrest ... and liable to imprisonment".

A police source said officers had been under strict orders to arrest people who made anti-Jewish statements or gestures.

The crowd turned out on Saturday with many holding Palestinian flags and the red banners of the far-left New Anticapitalist Party, which had called on people to defy the ban.

"Israel, clear out of Palestine, the era of settlements is over" and "Israel assassin, Hollande accomplice" were some of the slogans shouted by protesters.

After an initial peaceful start, police began firing tear gas when some hooded protesters threw cans and other objects at them, and several journalists covering the event were roughed up.

Some 2,000 police were mobilized, and many of them were present on the square to stop the rally from moving on to other parts of the French capital.