The activist group Autonomous Action, which organised the protest, said in a statement there had been "insistent requests from police and prosecutors to camp participants ... not to make a fuss and to avoid speaking to journalists."

The group said the raid on the camp on Saturday, which left one protester dead and seven others in hospital, was "not carried out by ordinary hooligans, but was a planned attack by Nazis."

Russian prosecutors said in a statement that at least 13 people attacked the camp site near Angarsk in the early hours of Saturday with bats and knives and that 11 of them aged between 16 and 22 have been detained.

But prosecutors also said that the activists were not environmental campaigners taking part in a protest against uranium enrichment at Angarsk but were instead anarchists preparing for a gathering at the end of the month.

One protester, Igor, contacted by AFP on Saturday, said that the raid was carried out by "skinheads" and that the camp had been set up as part of efforts to block plans to expand uranium enrichment at the facility.

Igor said local police had visited the camp, which was set up on July 14, at least four times in recent days to conduct document checks and had asked the activists to leave.

The statement from the prosecutors said the raid was likely carried out by local men taking revenge for the beating of one of their friends by activists from an anti-fascist movement who the attackers claimed were in the camp.

Prosecutors have opened a criminal probe into the attack on manslaughter and hooliganism charges. Charges for hate crimes carried out by political extremists carry heavier prison sentences in Russia.