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 labor 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 meter (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.