A human rights group says tens of thousands of orphans in Russian state institutions live in appalling conditions and are systematically deprived of basic rights.

In a report, the New York-based Human Rights Watch documented physical and psychological abuse of children which it said was so severe that it stunted their development and relegated them to a social underclass.

Disabled children -- who were deemed incapable of being educated -- were said to be especially neglected and spent their lives locked in dark rooms, or in their beds.

The group said the abuse could not be blamed on Russia's economic crisis and said many improvements could be made without spending money.

It said Russia should aim to remove as many children as possible from state institutions and provide other forms of upbringing, such as day care, foster families and small homes where children were encouraged to reach their potential.