Associated Press

Drivers put snow socks onto their cars during a heavy snowfall at the toll stations of Malgara near the Greek port city of Thessaloniki.

Sofia - Swollen rivers in Bulgaria and Greece burst their banks on Tuesday, leaving dozens of homes under water, as Bulgarian officials declared a day of mourning for eight people confirmed killed after a dam collapse nearly washed away their village.

Bulgaria's civil defence agency warned that two bigger dams were also on the brink of spilling over and residents were urged to prepare for an evacuation. Authorities have started a controlled release of water from the dams to prevent overflow.

Europeans across the continent have been battling more than a week of extreme weather, with thousands still trapped by snow in remote, mountain villages in the Balkans; hundreds - most of them homeless - dead after temperatures hit as low as minus 33 degrees Celsius; and authorities now facing the prospect of flooding caused by melting snow.

A day after the dam burst, the Bulgarian government declared a day of mourning, and streets in the village of Bisser were covered with sticky mud as people returned to their water-logged homes.

At least a dozen houses had collapsed, uprooted trees blocked roads and smashed cars sat abandoned along deserted streets. Veterinary officials were collecting the bodies of dead animals from streets still covered in snow.

Bisser Mayor Zlatka Valkova said she received a phone call about the dam and tried to get out of her office in time to alert people of the 2.5m torrent.

“I rushed out on the street, but then I saw the wave,” she said. “It was terrible, it came with such speed that I couldn't do anything.”

The village's 800 residents have been provided with food, water and medicine while the recovery operations continue. District Governor Irena Uzunova said eight people have been confirmed dead, and the whereabouts of an elderly couple remain unknown.

Bulgarian President Rosen Plevneliev and the EU commissioner for humanitarian aid, Kristalina Georgieva arrived on Tuesday to assess the extent of the damage.

“The next two weeks will be very difficult and the melting snow could make the situation very complex,” Georgieva told reporters in Bisser.

Georgieva voiced sympathy over the loss of lives and of property of people “who had not been wealthy even before the disaster”.

Further south, the heavy rain caused the Maritsa River to overflow its banks, leaving dozens of homes under water in the city of Svilengrad near the Greek border. Rescue crews helped transport nearly 100 residents to temporary shelters.

In Greece, rescuers had to help five elderly people escape from their flooded homes after the river Evros burst its banks near the country's north-eastern border with Bulgaria. Several elderly residents were also evacuated overnight from another three villages in the area.

Greek civil protection authorities said a 40-year-old woman was drowned by a flash flood on the eastern Aegean Sea island of Symi late on Monday, but no major damage was reported on the island. Heavy snowfall was reported across northern Greece, hampering road traffic and causing some power cuts in remote areas.

The Geneva-based World Meteorological Organisation said Tuesday that an incursion of cold polar air from northern Russia brought extremely low temperatures over large parts of Europe.

The cold air was fed with strong moisture from the central Mediterranean Sea, causing heavy snowfall over parts of south-eastern Europe.

Snow also caused headaches further north. Serbian emergency officials said the army will use explosives to break up ice on the Danube and Ibar rivers to try to prevent the possibility of flooding.

A 30-year-old woman died when large pieces of ice and snow collapsed on her in a suburb of the capital, Belgrade.

In Poland, meanwhile, the big freeze killed another six people in the last 24 hours, the Interior Ministry said in a statement. Ministry spokesperson Malgorzata Wozniak said on Tuesday that three other people died of asphyxiation with carbon monoxide from heaters they were using in their homes.

Heavy snowfalls trapped dozens of cars on motorways in south Ukraine on Tuesday and emergency officials deployed a helicopter to rescue the crew of a cargo ship stranded in icy waters in the Sea of Azov.

Ukraine, the hardest-hit country, has recorded 135 deaths from the cold, along with more than 2 150 people hospitalised with hypothermia and frostbite.

Lithuanian officials said 23 people have died so far this year due to subfreezing temperatures in the tiny Baltic republic of three million.

Montenegro's capital, Podgorica, was hit by strong winds that blew off roofs from houses, pulled out trees and traffic signs, turned over garbage containers and left parts of the city without electricity.

In the Croatian town of Split, on the Adriatic coast, authorities said the local hospital is overcrowded with people who sought help for injuries sustained in falls because of ice and snow. Split is unused to snow and usually has mild winters.

Italy remained in the grip of a bitter cold spell, with reports of people freezing to death. Low temperatures have even caused parts of the Grand Canal in the lagoon city of Venice to freeze over, while the south of Italy, which usually enjoys a mild climate, has seen snow that has caused power outages to thousands of people.

In Romania, snow and high winds have cut off 127 communities and blocked 237 county roads, and 1 100 people were stranded overnight in two trains. Ambulances were blocked by snow and unable to reach 32 snowed-in residents, including a woman in labour in need of help, according to health officials. An electricity company said 60 000 people have suffered power outages. - Sapa-AP