A teenage oligarch's son told how he wanted to 'expel the devil' from his mother when he strangled her to death with the cable of a phone charger in a Russian hotel.

Egor Sosin, 19, claimed minutes after killing her that his mother had wanted to have sex with him, and he had refused, before he brutally attacked her, according to a new witness.

Gruesome new details have emerged over the murder of 44-year-old Anastasia Novikova-Sosina, ex-wife of construction mogul Igor Sosin, in a blood-strained hotel suite in the Volga River city of Kazan.

Killed: Egor Sosin, 19, attacked his mother Anastasia Novikova-Sosina in a hotel in Kazan in December

Brutal: Soisin claimed Ms Novikova-Sosina (pictured) had wanted to have sex with him, and that he refused before he attacked her in the five=star suite in the city of Kazan, in central Russia

Fears: Ms Novikova-Sosina - whose former husband is construction mogul Igor Sosin - had decided to take her son with her to the hotel because she was worried about his drug use, according to a friend

Sosin, who said on social media he was a student at the Hult International Business School in London, is reported to have told state investigators: 'I had been choking her about half an hour. Satisfied that she had died, I sat on her and began to punch her with all my force.

'I hit her in the face. There were not less than 20 hits, they were strong.

'I cried when I hit her, and I was well aware that with my actions I was killing my mother.

'I bit her into the neck on the right side and felt the blood in my mouth.

'I saw blood running from my mother's face from my hits.'

Now LifeNews - which has close links to law enforcement in Russia - has reported that the teenager gave his first explanation of why he killed his mother to staff from five star Korston Hotel when they entered the room where the mother and son were sharing in December.

Hotel manager A. Mananov told investigators: 'He said that the woman was his mother.

'According to him, she tried to persuade him to be intimate, and gave some pills. Sosin said that he refused to have sex, and then expelled the devil out of her.'

It has been reported that a 'preliminary finding' of paranoid schizophrenia was diagnosed after psychiatric examination of Sosin junior.

As yet there has been no official comment on his mental state.

Violence: Sosin (pictured) told investigators he choked her for half an hour until he was satisfied she was dead, before starting to hit her with all the force he could muster

Terrifying: Sosin, centre, revealed 'I bit her into the neck on the right side and felt the blood in my mouth'

Gruesome: Ms Novikova-Sosina's body was discovered in a blood-soaked room after her son was found wandering the corridors of the hotel in just his underwear

If such a diagnosis was confirmed, and accepted by the court, he would not face trial for murder, or go to jail, because he was not responsible for his actions.

Instead he would be ordered to undergo treatment in a psychiatric hospital.

However, the court will have to examine testimony from the wealthy teenager which suggests he knew he was killing his mother.

In his first comments on the killing, tycoon Igor Sosin said he had been in close contact with his ex-wife over their concerns for their son.

The boy's mother had told him the teenager's behaviour was 'not quite sane' and that he was 'obsessed with delusions of persecution'.

He told investigators: 'I regularly called Egor, to be sure that he was sleeping at home.

'On one occasion, the way he spoke seemed to me messy, so I decided that he had some inadequate condition.

'And then I got a call from Anastasia. She said that Egor had had a party in their apartment and they used the laughing gas and 'mushrooms' there.'

Horror: Sosin revealed to investigators he watched as his mother's blood ran from her face

Weapon: The authorities believe Ms Novikova-Sosina was attacked with a mobile phone charger cable, like the one above in the room

Sick: He has since been found been found to be mentally ill by experts, and may therefore not be imprisoned

An anonymous psychologist has revealed that Egor's mother consulted her less than a week before her tragic death.

'In the last conversation Nastia (Anastasia) immediately confessed to me that she found out something terrible - her son was using drugs.

'It became evident when Egor arrived to Moscow from New York.'

The psychologist added: 'She noticed that her son behaved in a strange way. He didn't actually hide anything from his mother.

I cried when I hit her, and I was well aware that with my actions I was killing my mother. I bit her into the neck on the right side and felt the blood in my mouth. I saw blood running from my mother's face from my hits.

'She was scared to leave Egor alone.

'That's what she actually said: 'It's impossible to leave him unattended. His father isn't in the city. Egor has some strange friends, and am afraid they will take everything out of the apartment while I'm away'. That's why she went to Kazan with him.

'I started asking her if she tried to cure Egor. Nastia said: 'He went through detoxification from drugs'.

'And I said that the procedure won't be of much help, especially if keeps taking them.

'She said: 'He needs to be treated'. She asked me to find a good clinic'.

'Nastia said that she asked her son about which drugs he was taking. He said: 'These are just hallucinogens'.

'Nastia was also saying that there were some ball-shaped pills all over the apartment.

'Anastasia was angry, and couldn't believe that her beloved son could become a drug-addict.

'Their relationships started deteriorating when Nastia found out about those strange pills.

'She started having arguments with Egor when she found about the pills, telling him: 'You're a big boy, this is disgusting' and such.

'He was very angry with her.

'Her son started being aggressive towards her. I warned her: 'It's dangerous to stay with him on your own. Leave'.'

Warning signs: A friend has revealed how Sosin began to get aggressive towards his mother

Help: She had been discussing getting her son treatment ahead of the ill-fated trip to Kazan

She stressed: 'I begged Nastia not to argue with her son, not to touch him, or talk to him.'

It is said at the time of her murder, Ms Novikova-Sosina was seeking treatment for her son over his alleged drugs habit, say the Russian media.

The teenager told police his mother had given him medication, which resulted in hallucinations.

'I met with my mama for some medical procedures,' he said.

'She gave me some pills and later in the apartment, in our hotel, some unclear things started happening, hallucinations, as I am still feeling now.'

Witnesses say that on the day of the arrest they heard mother and son arguing so loud that people wanted to call the police.

The authorities were finally called when staff at the five star Korstan Hotel called police after finding Sosin walking around in only his underwear on Saturday.

Police arrived shortly afterwards, and 'found a young man strongly intoxicated with drugs', a law enforcement source from the regional branch of the Interior Ministry revealed.

'A woman with signs of violent death was found in his room,' the source continued.

Blame: The teenager told police his mother had given him medication, which resulted in hallucinations

'The police found out that the woman and the young man arrived from Moscow in the afternoon, rented a room, and in the evening the young man beat up and suffocated his mother during an argument.'

Police have said they were investigating the possibility that Ms Novikova-Sosina had been strangled with something like a mobile phone charger, after pictures of a similar object appeared on Russian television.

Sosin Senior is famous as a co-founder of Starik Khottabych, a renovation and construction giant, and is often seen on the Cote d'Azur resorts.