The two suspects, “put a gas mask onto the suspect’s head and covered up the air hole,” investigators said in a statement.

“In this way, the officers were trying to get testimony using an illegal method.”

The 31-year-old man, a resident of the town of Sludyanka on the shore of Lake Baikal, died after being questioned in a murder case in October, investigators said.

The suspects, who carried the rank of lieutenant and captain, told relatives that the victim died of a heart attack at the station, but a post-mortem showed that he died of asphyxiation, investigators said.

Russia’s ill-paid police force is widely feared for brutality and bribe-taking.

In a particularly shocking case last year, a policeman was charged with beating and raping a detainee with a curtain rail at a drunk tank in the Siberian city of Tomsk, leading to his death from internal injuries.

Last year, President Dmitry Medvedev announced a crackdown on the “evil” of police corruption and said that high-profile crimes by police had undermined their authority.