A Russian teenager who was 'blinded by rage' killed then beheaded a friend who had sexually assaulted his girlfriend, say police.

Nikita Rasskazov, 16, killed 19-year-old Artyom Shustov, then took his head in a plastic bin bag to show his girlfriend, Olena Matsneva, to 'prove' his love for her.

The Russian - known for being 'very calm' - has confessed to murder, during which he stabbed Shustov with a kitchen knife before beheading him in a park in Komsomolsk-on-Amur in eastern Russia.

He said that he deeply regrets the gruesome act, for which he faces up to ten years in jail.

Nikita Rasskazov (pictured), 16, has confessed to killing 19-year-old Artyom Shustov in Komsomolsk-on-Amur, Russia

A 14-week probe by the Russian Investigative Committee, equivalent of the FBI, found that his girlfriend, 17-year-old Olena Matsneva, had told Rasskazov how at a party Shustov had molested her after she refused to have sex with him

Matsneva told Rasskazov that Artyom Shustov (pictured) and another male friend had touched her breasts and genitals as she was held by another young woman

A 14-week probe by the Russian Investigative Committee, equivalent of the FBI, found that his girlfriend, 17-year-old Matsneva, had told Rasskazov how at a party Shustov had molested her after she refused to have sex with him.

She told Rasskazov that Shustov and another male friend had touched her breasts and genitals as she was held by another young woman.

This left Matsneva 'humiliated', but she did not report the alleged sexual assault to police.

Prior to the killing, Matsneva had posted a 'spooky' picture of herself and Shustov, believed to be from the party where she complained about the sexual attack.

Rasskazov said he had not intended to kill or behead his friend, but wanted him to apologise to his girlfriend for the sexual assault.

Rasskazov said he had not intended to kill or behead his friend, but wanted him to apologise to his girlfriend for the sexual assault. The talk turned into a fight, Rasskazov became 'blinded by rage' and beheaded his friend

The teen said he decapitated Shustov (pictured above), picked up the severed head by the hair, and put it in a plastic bag which he stashed in his backpack

The altercation took place at a park (pictured above) in Komsomolsk-on-Amur in eastern Russia

The talk 'turned to quarrel and then a fight', and the 16-year-old stabbed his older friend to death.

Then 'blinded by rage' he decapitated Shustov, picked up the severed head by the hair, and put it in a plastic bag which he stashed in his backpack.

He disposed of the rest of the body in bushes and hid the head overnight in his wardrobe with his bloodstained clothes.

The next day, he took the head to show his girlfriend, who was 'distraught' over the killing.

Rasskazov was trying to 'prove his love' to Matsneva by showing her the severed head, according to The Siberian Times.

Prior to the killing, Matsneva had posted a 'spooky' picture of herself and Shustov, believed to be from the party where she complained about the sexual attack

The alleged sexual assault by Shustov (pictured above) left Matsneva 'humiliated', but she did not report it to police. A photo of Shustov's chest tattoo also appeared on Matsneva's social media account

After showing Matsneva the severed head, Rasskazov then threw it into a local river.

Because he is under 18, Rasskazov faces a maximum ten-year sentence if convicted.

Matsneva's mother, who has not been named publicly, has spoken of how her daughter was in love with Rasskazov.

'My daughter literally blossomed when she began to date with Nikita,' she said. 'She was very worried if they quarrelled.

'He often visited our house, and was a very calm and quiet guy. I even wondered why my daughter chose Nikita rather than another lad. She said that Nikita was the best.'