The temperature in Ukraine sank to minus 33 degrees Celsius, the coldest in six years, while eastern Bosnia experienced lows of minus 31C and Poland, Romania and Bulgaria minus 30C.

Forecasters said the cold spell would last until Friday, with further heavy snow expected across the region on Wednesday.

At least 30 people, most of them homeless, have died in Ukraine in the past five days, the country's emergencies ministry said, while another 500 people were treated in hospital for frostbite and other cold-related ailments.

January temperatures in Ukraine do not normally sink below minus 15C.

The ministry said 1,600 centres had been set up to provide shelter and to hand out food for the homeless.

Five people died in Bulgaria and eight in Romania, where troops were called in last week to rescue hundreds of people stranded in cars by blizzards.

The Black Sea was frozen around the Romanian resort of Mamaia, and across the border in Bulgaria, a salt lake froze for the first time in 58 years.

Five people were reported dead in Poland overnight, bringing to 15 the number to have died since temperatures dropped at the weekend.

Several suffered carbon monoxide poisoning from old or faulty heaters, the Interior Affairs ministry said.

At least three people have died in heavy snow in Serbia's mountain regions to the south and south-east.

Authorities declared a state of emergency in 13 municipalities and deployed the army and firefighters to get supplies to remote villages.

"The situation is gradually being restored to normal," said Predrag Maric, head of the Interior Ministry's emergency situations department.

Dozens of villages were cut off by two metres of snow in eastern Bosnia, where the frozen body of a man was found at the weekend.

- Reuters