The Federal Penitentiary Service said today that the brawl was instigated by inmates who had just arrived at the prison colony outside Nizhny Novgorod on the Volga River.
Authorities said the inmates set fire to two facilities and broke furniture but did not mention the motive of the rioters and insisted they were fighting other inmates.
The Interfax news agency quoted a state-appointed rights commission as saying prisoners at the facility have complained about "unlawful" actions of officials there before.