Thousands of demonstrators marched under massive police presence in Paris on Thursday to demand that President Francois Hollande scrap labour reform plans that have sparked months of protests marked by serious violence.
More than 2,000 police enforced strict security measures around the capital's Place de la Bastille square to control the march, checking bags and turning away people with helmets or face-masks.
Police said 85 people were arrested as crowds converged on the marching zone.
The Socialist government originally banned the march but, facing a backlash within its own traditional support base, it backed down and allowed it.
But President Francois Hollande said his government would not retreat from labour legislation that will make hiring and firing easier in a contested attempt to tackle an unemployment rate that has been stuck at 10 percent for most of his time in office.
"We will take this bill to the finish line," Hollande told reporters as thousands of protestors marched in summer heat along a short protest circuit patrolled by more than one riot police officer per metre (yard).
In a months-long stand-off, neither side wanted to cave in and lose face over a reform plan that opinion polls say is opposed by more than two in three French voters.
"A majority of French people say it (that they oppose the reform). The majority of unions say it, and there's no majority in favour of it in the National Assembly (lower house of parliament)," said Philippe Martinez, leader of the hardline CGT labour union.
The march tested police forces already stretched under a state of emergency imposed since deadly attacks by Islamist militants in November and by fan violence at the Euro 2016 soccer tournament France is hosting.
The protests against a legislative bill that would loosen protection of worker rights pit Hollande's unpopular government against the CGT, which is also fighting for a place as France's most powerful union.
Hollande says the reform is key to hauling down double-digit unemployment, something he has promised if he is to run in next year's presidential election.
CGT leader Martinez accused Prime Minister Manuel Valls of pinning the blame for the escalating disorder on his group. He condemned the rioters but said the government had inflamed passions as unions sought a deal on the labour reforms.
"Every time we try to calm things down the prime minister throws fuel on the flames again."
Previous protests have been marred by hundreds of mostly masked youths engaging in running battles with police, hurling paving stones, smashing shops and plastering anti-capitalist slogans on buildings. Police have said some CGT members were in involved in the violence.