Russia's military has been tarnished by a series of scandals

The command of the interior ministry unit denied the claims made by the Soldiers' Mothers human rights group.

The group says it was contacted by a parent of a conscript who had been forced to work as a male prostitute.

Last year, an 18-year-old soldier was so badly beaten that he had to have his legs and genitals amputated.

The BBC's James Rodgers in Moscow says the latest claims follow a series of scandals which have damaged the Russian army's reputation.

A spokeswoman for the Soldiers' Mothers, Ella Polyakova, told the BBC that in St Petersburg there was "a network of clients" who would pay for sex with soldiers.

Older servicemen are said to have forced younger conscripts into prostitution and then taken the money for themselves.

Brutality

The Sychev bullying case drew worldwide attention to Russian army abuses.

Private Andrei Sychev was forced to squat for several hours by fellow soldiers and then tied to a chair and brutally beaten up last year.

As a result he developed gangrene in his legs and genitals, which had to be amputated.

Now permanently disabled, Pte Sychev has just announced that he is to write a book about his ordeal.

Such cases have highlighted the appalling conditions suffered by some Russian service personnel at a time when Russia is seeking a greater role on the world stage, our correspondent says.