The bus, with 22 passengers aboard, was crossing the river Yenisey in the Tyva republic but proved too heavy and dropped into two and a half metres (eight feet) of water.

Traffic regularly crosses frozen Russian rivers in winter.

"Two people were found dead, 20 others were rescued," the ministry told AFP.

On Tuesday six people died in a similar accident when a minibus fell through the ice of a frozen river in the western region of Nizhny Novgorod.

Russia has been in the grip of an extreme cold spell since the beginning of the week, resulting in several weather-related deaths and injuries from falls on icy surfaces.