Ice-breakers Tuesday battled Europe's big chill as the Danube river froze over more than 100 miles (170 kilometres), and dozens died of cold on a continent gripped by some of the lowest temperatures in decades.
The overall death toll from the cold snap that began 11 days ago topped 400 while forecasters warned there would be no early let-up to the freezing weather.
In Serbia, ice-breakers were summoned from Hungary in an attempt to keep the Danube flowing, while army demolition experts sought to dynamite ice barriers that threatened to provoke flooding on tributary rivers.
The Danube, one of Europe's main rivers, was barely navigable around Belgrade and the port authority in Veliko Gradiste, near the Romanian and Bulgarian border, said river traffic was blocked along a 170-kilometre stretch.
"I have some 30 vessels blocked in Veliko Gradiste," an official said.
In Bulgaria the Danube exploration agency said icing was at 20 percent near the Serbian border and up to 80 percent along a 220-kilometre stretch between the ports of Nikopol and Silistra further down river.
Navigation was impossible, the agency said, adding that the Danube delta leading into the Black Sea in Romania was completely frozen.
Upstream in Hungary, 13 ice-breakers went into action but only managed to clear the ports of Baja and Gyor.
"If the temperatures continue to be this low the ice could solidify on the Danube during next week as is already the case for smaller rivers," Istvan Land, director of Hungary's government water and environment agency OMIT.
Meanwhile, snow blanketed much of the Balkans with Serbia reporting 70,000 people trapped in villages in the south of the country.
A train linking Croatia's central coastal town of Split to the capital Zagreb derailed as a result of a snow drift. There were no reports of injuries.
The army and rescue services attempted to get food and medicine to hundreds of Croatian villages blocked by snow.
"This is a disaster, we have been cut off from the rest of the world ... Snowploughs cannot reach us, so we have to walk to get some bread and basic things," Marko Ancic told the Slobodna Dalmacija daily after trekking some 17 kilometres from his village to the nearest town.
Large parts of Bosnia were also cut off by the snow and avalanches.
Authorities have lost touch since Friday with the hamlet of Zijemlje, some 30 kilometres from the southern town of Mostar.
"We don't know what is going on there. They have not had electricity since Friday and phone lines are cut, they have no running water," Radovan Palavestra, the mayor of Mostar, told AFP.
Tuesday a woman was found dead of cold in a village near Mostar, while another was found by the roadside, covered by snow, near Travnik, in the centre of the country, police said.
Ukraine remained the country worst affected, with the death toll at 136, while the numbers killed by hypothermia in Poland rose to 68 after the authorities there recorded another six deaths in the past 24 hours.
The coldest place overnight was the Kvilda region of the Czech Republic where the mercury plunged to minus 39.4 degrees Celsius (-38.9 Fahrenheit).
The UN weather service said temperatures would remain low until March.
"We might expect the change in the current cold wave to to start easing from the start of next week up to the end of the month," Omar Baddour, a scientist at the World Meteorological Organization, told reporters.
In France, electricity consumption reached a historic high on Tuesday, the RTE powergrid company said.
In the Netherlands, a 55-year-old man drowned when ice gave way in Rijpwetering, in the west of the country, officials said.
Snow also kept falling in northern Italy, with temperatures dropping to minus 25 degrees Celsius on the shores of Lake Garda.
A woman froze to death in Monza, near Milan, on Tuesday, as did a mentally ill man who had wandered off from the institute where he was being looked after in the Campania region.
A homeless man was found dead under a cardboard shelter in Ferrara, while a woman who had been admitted to hospital days ago died of hypothermia.
In the town of L'Aquila, devastated by an earthquake in 2009, snowed-in residents warned of wolves scavenged in the deserted streets of the nearby village of Trasacco, the Corriere della Sera daily said.
Meanwhile, the Russian Gazprom company Tuesday said it was unable to meet a spike in requests for gas brought on by the cold, noting that demand has increased by 50 percent.