A 22-year-old man lost his hand and several others were injured as police tried to break up an unauthorised rave party in western France, authorities said on Saturday.
Five security officers were wounded in the clashes, prefect Emmanuel Berthier told reporters at a press conference.
The tensions erupted in a field near the Brittany town of Redon on Friday night.
Police repeatedly fired tear gas and charged clusters of violent partygoers who hurled metal balls, gasoline bombs and other projectiles at security forces, according to Berthier.
Local authorities estimated about 1,500 people took part. More than 400 officers were mobilised for the operation.
The rave party was held in tribute to Steve Maia Caniço, a young man who died in western France at a techno concert. The 24-year old fell into the Loire river as police intervened to shut down the party, prompting criticism over their heavy-handed approach.
Berthier accused the attendees of "extreme" and "inexcusable" violence. It took police more than seven hours to disperse the crowd, and authorities were still evacuating people from the field Saturday morning, Berthier told reporters.
He said an investigation is underway into the overnight events, including how the 22-year-old lost his hand.
Regional gendarme chief Pierre Sauvegrain told France Info radio that the man was believed to have picked up an object that exploded, without elaborating.
An underground New Year’s Eve rave party in the same area drew at least 2,500 people and led to multiple arrests.
France has been gradually lifting restrictions in recent weeks as infections wane and vaccinations rise.
France's curfew, among the strictest and longest in Europe, is set to expire Sunday. It has prompted growing frustrations among young people.