A 23-year-old man has been brutally tortured and killed by his friends in the city of Volgograd in southern Russia after revealing that he was homosexual.

The perpetrators reportedly inserted beer bottles in his private parts and cut his penis. Investigators say the victim's head was smashed with a 20 kg rock, making it difficult for the authorities to identify the mutilated body.

In a rare admission, local authorities in Russia said the incident was a product of hate crime.

The man was drinking with two of his friends aged 22 and 27 when the attack took place. His friends pounced on him as soon as he revealed he was gay, according to police. "The motive for the crime was the [victim's] non-traditional sexual orientation," said senior official Andrei Gapchenko.

While two suspects are in police custody, a witness has also been got hold of. Local reports said the attackers even attempted to burn the body.

One of the suspects, who has a criminal record, has allegedly admitted to the crime. Investigators have launched a murder probe and the two men could face up 15 years in jail if found guilty.

Russian authorities seldom attach homophobic motives to such incidents. Gay rights activists are pressuring the authorities for a more vigorous probe into such attacks which have sent shock waves in the gay community.

Reports suggest similar incidents have taken place in the same city in 2008 and 2012.

Although Moscow says it defends the rights of homosexuals, violations have been widespread across the country, according to reports.

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