Five police officers were injured overnight in western France as they broke up a 1,500-strong illegal rave, authorities said Saturday, with one party-goer losing a hand in the clashes.
There were "very violent clashes" when 400 police intervened, local prefect Emmanuel Berthier said, adding the violence lasted more than seven hours through the night.
"An evacuation operation is underway at the site," the prefecture tweeted later.
Police detained five men on Saturday and opened an inquiry into violence against people in positions of public authority.
Two of the five injured police officers had to be taken to the hospital in Redon, Berthier said.
He said the "people had an objective, to confront the forces of public order".
A police officer said it was not usual for people to bring the metal balls used in the French sport of boules or petanque to a rave.
Firebombs, metal balls, breeze blocks
Berthier told AFP that the group threw "Molotov cocktails, metal balls and bits of breeze blocks".
Two of the ravers were injured, including a 22-year-old man who lost a hand, local authorities said.
Event organisers said police had chosen violence instead of dialogue by firing tear gas grenades.
"It was war," said Flo, a 22-year-old man who attended the event.
"There hasn't been any music since last night," but "people taking part in the illegal rave are still on the scene," the prefect's office told AFP early Saturday.
Interior Minister Gerald Darmanin cancelled events he had planned and was regularly keeping abreast of the situation, aides said.
The rave had originally been set up in memory of a young man killed in nearby city Nantes two years ago during the annual nationwide Fete de la Musique celebration.
Prosecutors said Friday that Steve Maia Canico fell into the Loire river when police moved in to break up the gathering.
His body was found more than a month later and protesters in Nantes have demanded "Justice for Steve", saying the police intervention was disproportionate.
Hundreds of people flouted France's coronavirus curfew with underground parties near Dijon and a village in western Brittany, while police managed to prevent organisers from staging a major rave in Paris.