Thick ice on the Danube has forced Hungary to close the river to traffic, bringing shipping to a near standstill on Europe's busiest waterway.
The closure of the 2,860-km (1,780-mile) river on Friday came as the continent's death toll from extreme winter weather soared past 540.
The Danube, which was nearly wholly blocked from Austria to its mouth on the Black Sea, flows through 10 countries and is vital for transport, power, irrigation, industry and fishing.
"Shipping was ordered stopped overnight Thursday to Friday because of conditions created by icing along the Hungarian part of the river," said Istvan Lang, a Hungarian official.
"All ships still under way must immediately head for the closest harbour," Lang, quoted by MTI news agency, added.
Other countries along the Danube, including Austria, Croatia, Serbia, and Bulgaria, had already suspended river traffic because of the freeze.
In Hungary, 60 to 70 per cent of the river was frozen, with only ice-breakers remaining in action, especially in the south of the country, officials said.
Forecasters said the cold snap, which started two weeks ago, was expected to continue until mid-February.
Serbia's chief emergency official, Predrag Maric, told state television that the situation there was relatively better than in previous days as the snow had stopped.
He said emergency services would focus on delivering food to endangered regions.
Helicopters were to deliver food to remote areas of southwestern Serbia which have been trapped in snow for days, Maric added. Some 70,000 people were still cut off from the outside world.
Temperatures in Serbia hit a new low of minus 26 degrees Celsius on Friday in the northern town of Sombor and minus 15 degrees Celsius in Belgrade, the capital.
In Bosnia, 20,000 homes in the southern towns of Mostar and Nevesinje and surrounding villages were connected again to the electrical grid after three days without power, officials said.
"Shipping was ordered stopped overnight Thursday to Friday because of conditions created by icing along the Hungarian part of the river"
- Istvan Lang, Hungarian official
In Romania, 13 people died of cold overnight Thursday to Friday, bringing the overall toll to 57 there since the start of the cold spell, officials said.
In some villages, such as Varasti, in the south of the country, where four metres of snow have fallen, residents had to tunnel their way out of their homes or exit through top windows.
"I fear all my hens and turkeys are dead," said Varasti resident Marin Boacana, 60, pointing to his snow-covered chicken coop.
In Italy, where the cold has killed more than 45 in the past 10 days, snow was falling again on Friday, closing schools and causing disruption to travel.
A 42-year Romanian woman, believed to be sleeping rough and who had found shelter in a cave in the Rome suburbs, was found frozen to death, while a man was reported attacked by scavenging stray dogs near Rimini.
In Bulgaria where 32 have died, authorities continued a massive relief effort in the southeastern village of Biser, submerged under the icy waters of a nearby dam that burst on Monday. Ten died in the flood, with the last two bodies recovered on Friday from rubble.
At least 135 people have died of the cold in the Ukraine, 82 in Poland, 46 in Russia, 25 in the Czech Republic, 24 in Lithuania, and 16 in Serbia.
In France, the death toll increased to at least eight after Paris authorities said that two homeless men had died of cold in the capital over the past week.