At least 15 underground rooms full of human remains were uncovered

The prison, a former military barracks on the outskirts of the capital, Kabul, dates from the Soviet occupation of the 1980s, officials say.

A senior police officer in Kabul says that many of the bodies were found blindfolded with arms tied.

The find was revealed by a 70-year-old Afghan who worked for the Russians and only recently returned to the country.

There are at least 15 rooms full of dead bodies

Gen Ali Shah Paktiwal,

police chief

In pictures: Mass grave

There has been no immediate response from Russia to the news of the find.

"This is a big mass grave from the Russian days," police chief Gen Ali Shah Paktiwal told the BBC, adding that there were hundreds of dead bodies inside.

He said the base, on the northern outskirts of Kabul, belonged to the communist defence ministry.

"There are at least 15 rooms full of dead bodies," he said, adding that as the base was large there could be further rooms yet to be discovered underground.

Many of the victims' remains were found with rope or cloth around their eyes and hands, suggesting they had been blindfolded and bound.

The old man who led police to the site of the grave is reported to have told police that he had seen people killed by firing squad at the barracks.

The underground prison is the second Soviet-era mass grave to be found near the capital.

In 2006, a grave was discovered by Nato-led forces near the capital's notorious Pul-e-Charkhi prison.