Clashes have broken out between French police and demonstrators during a May Day parade in Paris.
Trade unions used the traditional march to protest against a proposed labour law to be discussed by parliament.
Police responded with tear gas when youths began throwing missiles, bringing the march to a standstill.
France has seen two months of unrest over the reforms. Several police officers were injured during countrywide protests on Thursday.
The proposed law, to be debated in parliament on Tuesday, would remove some of the protection workers enjoy against being laid off, in an attempt to encourage businesses to hire more people.
The socialist government says its aim is to combat chronic unemployment, but opponents say it will let employers bypass workers’ rights on pay, rest time and overtime rates.