In other cases, he showed up at his victims' doorstep, impersonating a social worker or a plumber. He would strangle the victims with anything at hand, such as a bathrobe belt, and take valuables.
The investigators, however, said that the pattern of his behaviour showed that he was not killing the women for the sake of material gain.
Tagirov, who was convicted of theft in 2009, reportedly killed his first victim in his hometown of Kazan but later expanded his activities to other cities on the Volga River hundreds of kilometres away, which earned him the nickname "the Volga maniac".
Police nearly caught the man in September 2011 when a victim's son walked in on the scene of the crime, but the killer escaped through a window.
One victim managed to survive but was unable to describe the killer as she was blind.
The murders had stopped by 2013, which led police to believe the perpetrator had died or was arrested on an unrelated charge.
Police offered $55,000 for any information leading to his arrest and spent years trying to link the killings by taking DNA samples from crime scenes as well as shoe prints and other evidence.
It took 10,000 genetic tests and countless cross-references to the police database to pin the crimes on Tagirov, the investigators said yesterday.
Tagirov has already confessed, investigators say, and is awaiting a court hearing to rule on his possible arrest.
