Scuffles broke out in cities including Paris, Nantes, Toulouse, Rennes, Grenoble and Montpellie, the Interior Ministry said in a statement
Riot police fired tear gas and water cannon at angry protesters marching on Thursday in France, in the latest outbreak of violence over the controversial new labour laws.
The law that will make firing and hiring easier was forced through in July. It is aimed at making France's protective labor laws more flexible.
Scuffles broke out in cities including Paris, Nantes, Toulouse, Rennes, Grenoble and Montpellier, the Interior Ministry said in a statement.
Hooded youths hurled bottles, beer cans and on occasion makeshift firebombs on the fringes of marches against the law.
"We are lifting our foot off the pedal for now. We are not going to do this every week," Jean-Claude Mailly, head of the Force Ouvriere union, told reporters at a rally in Paris's Place de la Bastille square.
Seven months from a presidential election, Mailly said that the unions would not let Socialist President Francois Hollande and his government off the hook.
"This law will be the chewing gum that sticks to the soles of the government's shoes," he told France 2 public television.
Mailly and Philippe Martinez, head of the CGT union, said they hoped legal challenges would force the withdrawal of the new law. They intend to challenge application decrees that will spell out exactly how the law applies on the ground.
Martinez said the law could be exploited by employers to trim overtime pay from a 25 per cent markup to 10 per cent.
Police said between 12,500 and 13,500 marched in Paris.
Some 62 people were arrested across the country, the Interior Ministry said. Fifteen gendarmes and police officers were injured, including two who were hospitalised.
The government hopes the law will help lower a jobless rate stuck close to 10 per cent.
(WION with inputs from Reuters)