Temperatures have plunged as low as minus 30 degrees Celsius (minus 22 degrees Fahrenheit) in the Moscow region and minus 60 degrees Celsius (minus 76 degrees Fahrenheit) in Eastern Siberia.

"Since the start of the cold, 123 people have died of exposure and frostbite," a medical source was quoted by the Interfax news agency as saying.

Another 833 people had to be hospitalised to be treated for hypothermia and frostbite, including 123 over the past 24 hours, of whom 14 were children, the source added.

Since the start of the cold snap, 1,745 people were affected, and more than 800 had to be hospitalised, the source said.