Alexander Semyonov said the detention brings the total number of detainees to 16 after masked assailants carrying baseball bats and metal rods attacked the camp in Angarsk, near Lake Baikal, which was protesting against nuclear waste imports into Russia.
Police opened an inquiry but suggested young neo-Nazis stood behind the attack in revenge for an incident in which several of their associates had allegedly been beaten up.
Western nuclear power companies have been sending byproducts from the uranium enrichment process to Russia, including 'unusable' uranium hexafluoride and uranium tailings, since the 1990s. Russia and Kazakhstan have also opened a uranium enrichment center in Angarsk near Irkutsk.
However, in late June Russia's nuclear chief, Sergei Kiriyenko, said Russia would not reprocess any foreign uranium tailings or waste from the enrichment process until safer methods were found. He added all existing contracts involving the Angarsk complex, the regional economic mainstay, would expire by 2010.