Nearly 300 protesters were arrested after May Day riots in central Paris, where hooded youths torched a McDonald's restaurant and several vehicles during a march against President Emmanuel Macron's public sector reforms.
Shouting "Rise up, Paris" and "Everyone hates the police", around 1,200 people in black jackets and face masks on Tuesday joined the traditional May 1 union-led demonstration for workers' rights, according to a count by Paris police.
After trying to hold up the march a group of protesters ran amok along the route, destroying a McDonald's restaurant near Austerlitz station, east of the city centre, and setting it ablaze.
They also torched vehicles at a car dealership, along with a mechanical digger and a scooter, leaving a trail of destruction and plumes of dark smoke billowing into the air.
The worst unrest in months in Paris comes at a time of heightened tensions over Macron's reform of the public sector and follows a showdown between police and anti-capitalist squatters at a sprawling commune in western France.
The police used tear gas and water cannon to disperse the demonstrators.
On Tuesday night, 102 people remained in custody out of 276 who were arrested, police said, adding: "31 businesses were damaged, of which two were burned, 6 vehicles were burned and 10 others damaged."
Macron condemned the violence, posting on Twitter during his trip to Australia: "Everything will be done so that the perpetrators are identified and held responsible for their actions." He added the demonstrations would be treated with "absolute firmness".
The police had warned of the risk of extremist groups using May Day to set up a rematch of the clashes seen during demonstrations last year over Macron's labour reforms and at an anti-capitalist camp in western France that was demolished by police earlier this month.
"Macron makes us mad," read a banner held by one masked demonstrator.
"We're tired of this capitalist system that destroys everything and of brutal police repression of all those who oppose it," a 19-year-old student who was part of the group told AFP.
The scenes of looting and destruction overshadowed the May Day march, which drew between 20,000 and 55,000 peaceful protesters according to police and union estimates.
Countrywide, around 143,000 people took part in labour marches, according to government estimates, up slightly on 2017.
Trade unions and students' unions have been trying to rally the French against Macron's shake-up of indebted state rail operator SNCF and access to public universities, which they see as part of a rollback of France's cherished public service.