Moscow - A retired Russian policeman was jailed for life on Wednesday for raping and murdering 22 women after he claimed he wanted to cleanse his Siberian hometown of prostitutes.Mikhail Popkov, who worked as a police officer at the time of most of the murders, raped and stabbed the women late at night in the city of Angarsk after offering to give them lifts in his police car, investigators said."Investigators managed to gather evidence implicating Popkov in 22 murders and two attempted murders of women," the Investigative Committee said in a statement after his sentencing.The victims' bodies were found dumped in woods, on the roadside and in a cemetery.A further two women managed to survive Popkov's attacks but suffered serious injuries.The victims included a teacher and a shop assistant as well as several prostitutes, Russian media reported.Self-styled 'cleaner'Popkov described himself as a "cleaner" who was purging the city of prostitutes, Rossiya 1 television reported."He drove out on the streets of the city at night looking for women. He either offered [his victims] a lift or the women flagged him down for a ride... Then the crime was committed, almost always according to the same scenario," prosecutor Olga Muzykova told Rossiya 1."By calling himself a cleaner, he was trying to justify himself," she added. "He was an ordinary serial killer."The wave of murders took place over six years, from 1994 to 2000, spreading fear among the city's residents, before suddenly ending.Investigators had suspected a policeman was behind the crime because of the way the killer carefully covered up his tracks.Popkov was caught after investigators re-examined the case and carried out DNA testing of residents, focusing on those who drove a car make whose tracks had been found at crime scenes.The murderer had taken part in investigating some of the crimes he has been convicted, said Komsomolskaya Pravda daily, citing his former colleagues.Popkov, who retired from the police force in 1998, was arrested in 2012 in the far eastern city of Vladivostok where he had gone to buy a car.Popkov will serve his sentence in a special prison colony for former law enforcers.