Unions are going to hold a short march on Thursday around the Bastille plaza to protest government plans to make workweeks longer and layoffs easier.
It may be recalled that some similar protests in the last few weeks had led to clashes between riot police and radicals.
Police threatened to ban Thursday's march, but the government agreed to let it proceed. Interior Minister Bernard Cazeneuve warned that "no violence will be tolerated."
Police have said some union members supported recent violence. But the head of the influential CGT union, Philippe Martinez, insisted on BFM television that "We are not accomplices of the troublemakers. We condemn them firmly."