Helicopters ferried food and medicine to iced-in villagers Wednesday as Europe's 12-day-old cold snap tightened its frigid grip on the continent, where more than 400 have died as a result.

Eastern countries such as Poland and Ukraine account for more than half of the death toll, and dozens more have succumbed to the weather's secondary effects, such as asphyxiation due to shoddy heating.

Heavy snows eased in Bosnia but the bitter cold continued, especially in the south and southeast where temperatures dropped to minus 20 degrees Celsius (minus 4 Fahrenheit.)

Thousands struggled without power, including around the historic city of Mostar, where some 15,000 homes had no electricity.

Uma Sinanovic, a spokeswoman for Bosnia's defence ministry, said areas around Nevesinje and Berkovici in the south were especially hard hit.

"The electricity has been down for two days, phone lines are also down in that region," Dragan Stark of the Bosnian Serb civil protection service said. "It's a disaster."

Bosnian authorities sent civilian and military helicopters to isolated hamlets near Mostar and Kalinovic, bringing much-needed supplies like flour and oil, and ferrying sick people to hospitals.

Authorities said two more people had died from the cold in the rugged mountainous Balkan nation, raising the toll to seven, while Albania reported its first victim, a man aged 37 found dead near Tirana.

Russian authorities said at least 110 people had died as a result of the cold so far this year, 44 of them in the first week of February alone.

"Weather like this (comes) only once in five years, it's usually much warmer," said Moscow resident Pavel Sterlikov.

Elsewhere, icebreakers were hard at work to clear parts of the Danube, one of Europe's main arterial waterways, with stretches of hundreds of kilometres frozen between Croatia and Bulgaria.

Serbia banned navigation along all waterways, including the Danube, Sava and Tisa rivers, because they were frozen, Beta news agency reported.

More than 70,000 people remained cut off from the outside world in Serbia and other Balkan countries. In southern Croatia more than 100 villages were isolated for the sixth consecutive day.

Miserable conditions persisted in Bulgaria, with violent snowstorms raging in the Danube plain in the northeast, where all traffic has been suspended since Tuesday and the main border crossing with Romania closed due to ice.

Four more people were found dead under snow in the Pernik region in the country's west, raising the death toll to 20 as authorities declared a national day of mourning for eight people drowned Monday after rivers flooded and a burst dam sent freezing waters into the village of Biser. Two residents are still missing.

Ukraine remained the worst-affected country, with hundreds of cars stranded on the Crimean peninsula and at least 131 deaths so far, while three more people froze to death in Romania, bringing that country's total to 41.

The Hungarian Central Bank, meanwhile, said it literally had money to burn to help the country's homeless. The bank has been pulping wads of its retired forint banknotes and turning them into briquettes.

Famished wolves scavenged in the isolated, snow-covered Italian village of Trasacco, while keepers at the Berlin zoo imposed a cold curfew on giraffes and antelopes, which will be kept inside for all but 2.5 hours each day.

In Gruissan, southern France, the weather was taking its toll on pink flamingos, with dozens dying as their feet get caught in iced-over wetlands.

Pope Benedict XVI urged Catholics and religious organisations to show solidarity and generosity to victims of the cold.

While conditions have been brutal for much of Europe, residents in the Netherlands were waiting with bated breath to see if the country's canals will freeze hard enough to allow a legendary ice-skating race to take place.

For the so-called Elfstedentocht (11 city) race to take place for the first time in 15 years, the ice needs to be at least 15 centimetres (six inches) thick along the entire 200-kilometre (124-mile) route.

Canals were also frozen in the heart of Paris, where city authorities brought out their only ice-breaker, a barge equipped with a snow plough, as French electricity consumption hit a new high.

In Germany, the cold allowed professional ice hockey team the Hamburg Freezers to hold their first-ever training session on the frozen Alster river amid reports of grave-diggers having to use pneumatic drills to break frozen ground and even penguins hiding indoors at a west German zoo.

The country, which decided last year to abandon nuclear power, was forced to bring several reactors back on line to deal with the peak in electricity demand, the daily Handelsblatt reported.

burs/mlr/fz