Some 2,500 partygoers attended an illegal New Year rave in northwestern France last night, violently clashing with police who failed to stop it.
The event sparked concern the underground gathering could spread coronavirus, authorities said today.
The revellers had set up the illegal rave in Lieuron, south of Rennes in Brittany after skirmishes with police, according to a statement from the local prefecture.
Many were still on the site today as a sanitary cordon was thrown up around it.
Local gendarmes tried to "prevent this event but faced fierce hostility from many party-goers" who set one of their cars on fire and threw bottles and stones, it said.
Those present had come from across France and even abroad, authorities said.
Such mass gatherings are strictly prohibited across France to prevent the spread of Covid-19 and a nationwide 8pm curfew - which was not lifted for New Year - applies across the country.
Reports said that the rave party took place in a empty warehouse belonging to a storage company.
Prosecutors have opened an investigation into the illegal organisation of a musical gathering and premeditated violence against persons in authority.
Vehicles registered from all over France were still parked at the site today and many revellers were present as techno music thudded away, an AFP journalist said.
Participants interviewed by AFP said that the revellers had included partygoers from foreign countries, including Spain and Britain.
One participant, who gave his name as Jo from the Alsace region of eastern France and refused to be identified further, said they had all met at a meeting point on Thursday evening in the parking lot of a shopping centre.
Then the convoy headed for Lieuron where the police tried to prevent them from passing, he said.
He acknowledged that "very few had respected social distancing" at the event, which was supposed only to end later tomorrow.
French authorities have been anxious about mass wildcat rave parties throughout the pandemic but New Year's night was a particular concern.
In the southern city of Marseille, security forces halted an illegal party grouping some 300 people, police said.
Over 150 people were warned and the three suspected organisers have been arrested.
Interior Minister Gerald Darmanin said that 132,000 police had been deployed across France for the New Year celebrations to ensure security and that the curfew was respected.
Also today, France announced it was imposing an immediate earlier curfew in 15 northeastern and southeastern departments to combat the spread of the coronavirus, starting at 6pm. This will be reviewed in a week's time.
France has the highest Covid-19 cases count in Western Europe and the fifth in the world, with 2,620,425 in total. The death toll is 64,632.
It has already brought in two national lockdowns. Those measures were eased in mid-December, but restaurants and bars are off limits for now and it is not clear when they might reopen, although 20 January was initially floated as a target date.
