Heavy snow has left at least 11,000 villagers cut off in remote areas of Serbia amid a European cold snap that has claimed more than 130 lives.
At least six people have died in Serbia, with emergency services expressing concern for the health of the sick and the elderly in particular.
Temperatures are below -30C (-22F) in parts of Europe and 63 people have died in Ukraine and 29 in Poland.
In Italy, weather experts say it is the coldest week for 27 years.
Emergency services in Serbia have described the situation, close to the country's south-western borders with Kosovo and Montenegro, as very serious.
In places, the snow has reached a depth of 2m (6ft 6in). Fourteen municipalities are affected, emergency official Predrag Maric told the BBC.
Helicopters have helped move several people to safety, and food and medicines have been airlifted to isolated areas.
Snow began falling in Serbia on 7 January and has hardly stopped since, says BBC correspondent Nick Thorpe. Serbian media say further snow is expected in the coming days.
Ukraine has seen the highest number of fatalities, many of them homeless. Over a 24-hour period, as many as 20 people died.
Food shortages have been reported in the capital, Kiev, because lorries have been unable to transport supplies.
Heavy snow has also caused widespread disruption in northern and central Italy.
More than 600 passengers were trapped on an unheated train in the Apennine mountains for seven hours on Wednesday night, when the brakes and electrical cables froze.
The coldest temperatures have been recorded in Russia and Kazakhstan.
In the Urals and Siberia, the temperature fell to -40C (-40F) while in the capital of Kazakhstan, Astana, a forecaster told Interfax-Kazakhstan news agency the wind-chill factor meant the real temperature was down to -52C, even though the air temperature was -35C.
In southern Russia, cars and lorries became stuck in snow drifts between Novorossiisk and Krasnodar.
Heavy snow has also hit Turkey, with 50cm falling in Istanbul on Wednesday. An avalanche in the south-east of the country killed a woman in her home, reports say.
Another avalanche blocked a main road connecting the provinces of Bitlis and Diyarbakir.
Rescuers in Germany were unable to save an elderly woman after she had gone swimming in the frozen waters of a gravel pit in Lower Saxony. Reports said she had often swum in the lake.