In Russia's Volga region, six people drowned when the ice broke under a minibus that was crossing a frozen river near the city of Nizhny Novgorod.
The minibus was driving on the ice at a place normally used in summer.
"There were 15 people in the vehicle, nine managed to escape and six drowned," an official with the emergency ministry told the Interfax news agency.
Interfax also reported two people had died of hypothermia in Moscow while another 14 were hospitalised with exposure.
More cold for Moscow
Forecasters said the cold snap in the Moscow region could reach as low as minus 37 C towards week's end, as local authorities implemented measures to ensure the smooth functioning of public infrastructure amid the sudden plunge in temperatures.
State schools said students did not have to attend as long as the temperature remained under minus 20 C in the morning, while buses in Moscow, Saint Petersburg and other cities were filled with special "Arctic" diesel fuel to minimise disruption.
Traffic policemen, omnipresent on Russian city streets, were issued with "emergency felt boots" while train stations and other public transport sites were told to let homeless people take shelter inside rather than being kicked out as usual.
The Moscow city government set up a special "headquarters to counter the Siberian freeze", while in Saint Petersburg emergency services were instructed to draw up plans for dealing with cold-related emergencies, the RIA-Novosti news agency said.
Moscow energy officials issued warnings to about 200 companies and other organisations whose energy supplies might be reduced in order to conserve supplies.
The MFB stock exchange suspended trading mid-afternoon after being among those warned of a possible power shortfall.
"The capital for the first time has come up against a situation where, due to the cold, its demand for energy may well exceed supplies," said Nestor Serebryannikov, the former head of the Moscow municipal power utility.
Power reliability
However a spokesman for the Moscow energy department, Vasily Zaharov, told RIA-Novosti that the city's power stations were "ready to work reliably during the cold temperatures".
An honour guard will continue to stand to attention at the eternal flame commemorating World War II beneath the Kremlin walls, a spokesman for the Federal Security Guard said.
"We of course take care of our soldiers," the spokesman, Sergei Levyatov, told ITAR-TASS. "But there won't be any felt boots. They're wearing woolly socks under their boots."
ITAR-TASS said 189 people had died in Moscow from the cold since October, of whom nearly 70 percent were in an inebriated state.
Extreme cold in several Russian regions was testing the often ageing
centralised heating systems that typically pump heat around towns and cities by means of underground pipelines.
In Komi province in northwest Russia, 83 people, including 66 children, were evacuated from their village after a heating failure that began on January 13, RIA-Novosti said.
In Samara region in southwest Russia's Volga region, a burst main left nearly 10,000 people without central heating or water, with the outside temperature at minus 36 C.
About 2,500 people in two villages in Siberia's Irkutsk province were left without central heating after a fault developed there on Monday.