Thick clouds of tear gas hung above the Place de la Nation square in Paris where youths in balaclavas and ski masks lobbed cobblestones and bottles at black-clad riot troops shouting: “Everyone hates the police.”
Police estimated some 17,000 protesters marched throughout the French capital for a rally riding a wave of anger against planned labour reforms set to come before parliament on Tuesday.
Ten people were arrested, while one demonstrator and one officer were lightly injured in the scuffles, police said.
The May Day rally was the second protest against the reforms in a week to descend into violence led by troublemakers known as “casseurs” (breakers) who actively seek confrontation with security forces.
Several other protests in recent weeks have descended into violence in cities across France.
While government hopes the reforms will reduce chronic unemployment of about 10 percent, critics believe they threaten hard-won workers' rights by making it easier to lay off people in lean times.
Government has already watered down the bill but this has failed to calm the anger among students and workers demanding it be withdrawn.
“Withdraw, withdraw, the labour law. Not amendable, not negotiable,” protesters chanted as they began marching from the Bastille square.
French Prime Minister Manuel Valls on Sunday warned groups of troublemakers known as “casseurs” (breakers) who appear on the sidelines of marches actively seeking confrontation with police, leading to violent clashes.
“We will respond with the greatest of determination to these troublemakers … the attacks and violence against security forces are unacceptable,” said Valls.
Labour Minister Myriam El Khomri meanwhile defended her reforms, saying that debate on the bill should now shift to parliament where it is due in two days.
“This bill is fair and necessary,” she told local media, adding that reformist unions who represent most workers were behind the changes.
Jean-Luc Melenchon, leader of France's Left Party and presidential candidate in 2017 polls, warned against the rising violence at demonstrations.
“At the rate we are going someone is going to die because violence is a little worse at each protest,” he said.