Protestors torched cars, looted shops and stoned police at the end of a rally against a youth labour law in the centre of Paris this afternoon.
Fire-fighters doused the front door of a six-storey apartment building set on fire in teh Rue Fabert close to the Foreign Ministry in the Invalides area in central Paris.
The trouble started despite a warning from the interior minister Nicolas Sarkozy that violence would be severely punished.
Police fired tear gas in an effort to contain the violence that erupted after thousands of students and workers marched through Paris, calling on Prime Minister Dominique de Villepin to withdraw his First Job Contract, which protesters say will create a generation of "throw-away workers".
Dozens of youths smashed shop windows with chairs, overturned a car, torched another vehicle and hurled stones at police.
Charlie Herblin, a 22-year-old worker who has protested in the past blamed the violence "young criminals". "This discredits the movement," he said.
Protests against the law have spread across France in the past few weeks, largely remaining peaceful, but violence has erupted in the centre of Paris after previous rallies.
Interior Minister Nicolas Sarkozy met union officials on Tuesday after one of their members fell into a coma after being hurt in violence after Saturday's Paris demonstration. Public prosecutors said there was no evidence police were to blame.
Mr de Villepin today invited France's unions to talks.
The proposed CPE law allows employers to fire people under 26 without giving a reason during a two-year trial period. The Prime Minister hopes the contract will help to cut youth unemployment.