Murder detectives investigating one of Russia’s worst ever serial killers have uncovered a series of grisly graves full of women’s remains.

Siberian beast Mikhail Popkov, nicknamed ‘The Werewolf’, was jailed for life over the rape and slaughter of 22 women.

The married ex-policeman, who sexually attacked his young victims and butchered them with axes, knives or screwdrivers, is 'singing like a bird' and confessing to killings not previously linked to him, say sources.

Murders: Russian serial killer Mikhail Popkov is already in jail for the slaughter of 22 women, but he is now confessing 'many' more to police officers - leading investigators to believe he could be the most prolific serial killer ever in Russia

Victim: Viktoria Chagaeva holds a picture of her 20-year-old sister Tanya Martynova, who was killed by Popkov after attending a concert with a friend in 1998

Innocent: Yulia Kuprikova, who was murdered with her friend Tanya Martynova after a concert in 1998

Popkov, 51, has directed police to human remains of women who had been reported as missing but whose fate was unknown until now.

On his arrest in 2012, the mass killer told police he wanted to 'cleanse the streets of prostitutes' in Angarsk, an industrial city in Irkutsk region, where he presided over his reign of terror.

Police refuse to put a total on the gruesome new discoveries of female victims because the 'long and painstaking' investigation is still continuing.

But it is now believed that Popkov's toll may even exceed his idol, the worst-ever Soviet serial killer Andrei Chikatilo, aka the Butcher of Rostov, who was convicted of 53 murders, and the more recent Moscow maniac Alexander Pichushkin, known as the 'Chessboard Killer', who killed 49.

Crucially, police have evidence Popkov's killing spree lasted at least five years longer than known at his trial which ended in January 2015.

As a policeman, Popkov was able to offer his trusting victims lifts home in his car at night, before taking them to remote locations where he killed them.

He then dumped their naked bodies in woods by the side of the road, many of which were never found again.

The victims included a teacher and a shop assistant as well as several prostitutes.

Senior investigator Andrei Bunayev revealed: 'The investigation will be very long because there are a lot of cases.

'He names the places where bodies are hidden. We find these bodies and check his involvement. He says very clearly when and what was done.

'We are looking for evidence that confirms his words. A large number of episodes are confirmed.

'So far I can only say that a lot of new episodes have been revealed. We will announce the exact number later.

Jailed: A former police officer, Popkov was able to evade capture for so long because investigators couldn't believe that the killer they were hunting was one of their own

Spark: According to investigators, Popkov began his killing spree after discovering contraceptives in the family rubbish bin - leading him to assume, wrongly, that his wife Elena (pictured) was having an affair

'Popkov left biological traces in some cases which were not studied earlier - but now there is an opportunity to examine them.'

He continued: 'He is collaborating with us. Everything he says is confirmed. He confidently guides us to the place where a body is found and explains what happened, what injuries he caused.'

It was previously believed that Popkov had ended his killing spree in 2000, when he claimed to suffer impotence after contracting a venereal disease from a victim.

But it has now emerged that some cases were just 10 years ago, while detectives have also dusted off files of unsolved murders dating back to the 1990s - over a vast area of eastern Russia.

Speculation in Russia has suggested that as many as 50 new cases have been revealed.

Family man: After Popkov was first accused, his wife Elena, 50, and daughter Ekaterina (pictured with Popkov), 28, refused to believe that he could have been capable of the murders

Escape: After the latest revelations about the 'many' new murders, however, they have moved to a different city to try to start a new life. Pictured, Ekaterina with her father

Caring: Popkov was able to hunt his victims so easily, as he would offer them lifts late at night in his police car. But he then drove them to remote locations where he raped and killed them, dumping their bodies

Pain: Speculation in Russia has suggested police are examining up to 50 new cases but police have refused to comment on the exact number that Popkov has now revealed to them. Pictured, Popkov's wife Elena

Popkov is expected to face trial for the cases that have now emerged later this year.

He was known to regularly drive between Angarsk and Vladivostok, on the country's Pacific coast - a distance of around 2,500 miles.

Two of his earlier victims were Tatiana (Tanya) Martunova, 20, and Yulia Kuprikova, 19, who were found dead on 29 October 1998 in an Angarsk suburb following a night out.

Tanya's sister Viktoria Chagaeva, 48, who owns a beauty salon in Angarsk, said: 'The pain does not go away. It was me who gave Tanya a ticket to go to a concert, and she was killed after attending it,'

Popkov's wife Elena, 50, and daughter Ekaterina, 28, a teacher, initially stood by him, refusing to believe he was a mass killer.

But since his trial they have moved to another city to begin new lives.

One theory is that he began his murder spree after, wrongly, suspecting his wife of cheating on him.

He found two used condoms in the rubbish at home, and this sparked his drive to take revenge on women, it is claimed.

In fact the contraceptives had been used by guests.

'I just had some reasons to suspect her,' said Popkov, of his belief that his wife had slept with another man.

'I'm not looking for excuses, but this was the impetus for my future.'

He admitted to having a negative view of women who went out at night to drink without their husbands or boyfriends.

Killed: It has not yet been revealed how many more women Popkov killed. Two of his victims were Tanya Martynova (right), 20, and Yulia Kuprikova (centre), 19, found dead on 29 October 1998 after a night out

Guilt: Tanya's elder sister Viktoria (pictured with her and their mother Lyubov) says the pain of her Tanya's loss never goes away - and it was Viktoria who bought her the concert ticket after which she was murdered

Appeal: A newspaper cut out of the police appeal for Tanya's friend Yulia Shapovalova after she went missing

Now he says: 'I had no right to evaluate people, their behaviour... this is my repentance.'

He evaded capture for years because police could not contemplate that one of their own officers could be a mass killer. He was finally captured after 3,500 officers were made to take DNA tests.

His daughter at first refused to believe he could be a murderer.

'I do not believe any of this. I always felt myself to be "Daddy's girl",' she said.

'For 25 years we were together, hand in hand. We walked, rode bikes, went to the shops, and he met me from school.

Dumped: A road near the town of Meget, Russia, where bodies of the two friends Tanya and Yulia were found

Home: Block of flats in Angarsk where Tanya lived - and failed to return after she was targeted by Popkov

'We both collect model cars, so we have the same hobby.

'I wanted to be a criminologist, so I read a book with tips of how investigators catch serial killers and there were also basic classifications [about murderers].