Police said at least 15 assailants raided a tent camp at the Yelovskoye Reservoir near the city of Angarsk occupied by a group of protesters against reprocessing of nuclear waste at a local plant.
"The attack on a tent camp occurred at 5.10 am Moscow time (1.10 am GMT) Saturday. At least
15 attackers raided the camp occupied by 21 environmentalists," the source said.
"A 21-year-old man was killed and seven people were hospitalized with injuries," he said.
Police said they have detained two suspects in the assault and identified at least 13 others.
A criminal investigation has been launched in connection with the attack.