Revellers Saturday left an illegal New Year rave in northwestern France that had drawn some 2,500 people, led to clashes with police and sparked concerns it could spread the coronavirus.

Police had failed to stop the underground event, set up on Thursday in two disused warehouses in Lieuron, south of the city of Rennes in Brittany.

Such mass gatherings are banned across France to prevent the spread of Covid-19, and a nationwide 8:00 pm curfew -- which was not lifted for New Year -- applies across the country.

Techno music had blared out during the night from the warehouses, which had been transformed into illegal nightclubs for partygoers who had flocked to the site from across France and even abroad.

The local prefecture said Saturday the music had been switched off and sound systems dismantled after two nights, and the first revellers began leaving the site before dawn.

By 10:15am the site was under the control of police, who had booked more than 800 people for failing to respect the curfew restrictions or wear masks or for "participating in an illegal assembly", it said in a statement.

Earlier Saturday, the prefecture said only "a few hundred" of the estimated 2,500 revellers remained, quoting an association that oversees the prevention and security risks of such events.

Interior Minister Gerald Darmanin tweeted that the large police presence at the site had led to the breakup of the rave "without violence".

Police on access roads were checking all those leaving the site, on foot or in vehicles, an AFP photographer said.

The officers were in particular on the lookout for narcotics, and were using torches to check the eyes of the ravers for signs of drugs use.

Police reinforcements continued to arrive and close off the site in a calm atmosphere Saturday morning, the photographer said.

About half of the car park at the site was empty early Saturday morning.

French authorities have been worried about mass rave parties throughout the pandemic, but New Year's Eve was a particular concern.

Police had Thursday night tried to "prevent the event but faced fierce hostility from many partygoers" who set one of their cars on fire and threw bottles and stones, the prefecture said on Friday.

First aid workers distibuted hand gel and masks to the revellers to try and limit the spread of the virus.

The French government, facing the threat of a new wave of Covid-19 infections, announced on Friday it is bringing forward its nighttime curfew by two hours in 15 regions to help combat the virus.

The country recorded around 20,000 new cases and 133 deaths on Friday, bringing the total number of fatalities to almost 64,800.

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