Kristina B (right) and Valeria K (left) confessed to killing their 'friend' Sofya Potapova after drinking session. Picture: Vkontakte

The two alleged killers - labelled 'teen monsters' - were detained in the Sovetsky district of Buryatia after the discovery of the body of the 16 year old girl. State investigators say that after believing they had suffocated Sofya to death, they ordered a taxi and propped up their friend in the backseat, pretending she was alive.

They 'lied to the driver telling him their friend passed out from drinking and that they needed to get to the river to get some fresh air'.

The two alleged killers - labelled 'teen monsters' - were detained in the Sovetsky district of Buryatia after the discovery of the body of the 16 year old girl. Pictures: Vkontakte

In fact, she then did show final signs of life and one of the girls then used her hands suffocate and finally kill the teenager. The taxi driver evidently didn't notice anything amiss and dropped the girls at a site close to the Selenga River.

A report by the Investigative Committee, responsible for probing serious crime, stated: 'In the course of interrogations (the girls) gave detailed testimony about the circumstances of the murder.'

'Sonya was brutally murdered, by her so-called 'friends'. Pictures: Vkontakte

Dmitry Stolyarov, an Investigative Committee official, said: 'The girls spent quite a lot of time sitting on the river bank and deciding how to cover the crime. When they saw a passersby, they sat the corpse of their friend between them and kept it there until the people left. Eventually, they dumped their victim's body on the shore and left the crime scene.'

The tragic events unfolded after the girls met in Ulan-Ude city centre and had a drink. They went to visit a male friend in the Kirzavod district of the city, but he was not at home, and they continued drinking in the yard of his flat.

'The girls got drunk and started arguing. Eventually, two of the girls pushed the third one to the ground and started suffocating her,' said one account.

'Obviously, the animal showed aggression because he's a predator.' Picture: Seversk Zoo

In a social media posting dedicated to the dead girl, a friend says her death has brought 'irreparable grief'. 'Sonya was brutally murdered, by her so-called 'friends',' said the post.

'Almost the whole day, they tortured and beat her. In the end she was brutally murdered. I decided to create this post so that all the caring people would know the faces of these spoiled, these seeds-of-the-devil teen-monsters'.

The names of the two detainees are given in full. The official investigation is continuing into the incident.