At least four Balkan nations suspended shipping on the Danube River because of severe frost and the vast amount of ice blocking the heavily traveled waterway.
Bulgaria, Croatia, Romania and Serbia made the decision because up to 90 percent of the river's surface is covered with floating ice, authorities said Wednesday.
The conditions are making it extremely difficult to traverse Europe's main commercial waterway, which winds 2,860-kilometer (1,777-mile) from Germany and serves as the natural border between Bulgaria and Romania.
Europe has been battling a deep freeze that started in late January and has killed hundreds, snow that has trapped thousands in Balkan mountain villages and prompted worries of flooding as heavy snow melts. In Greece and Bulgaria, flooding on Monday and Tuesday left dozens of homes under water and at least eight dead.
Serbian emergency officials have said the country's army will use explosives to break up ice on the Danube and Ibar rivers to try to prevent flooding.
The Sava and the Danube are partially frozen, with large chunks of ice floating down the two rivers. In some parts, ice on the Danube is 15 centimeters (nearly six inches) thick, but so far it hasn't jeopardized the work of Serbia's biggest Djerdap hydropower plant, near the Romanian border, officials said.
Serbia also banned any shipping along the Sava and Tisa rivers. An official, Milos Milovanovic said "the entire Sava river is blocked with ice, even around Belgrade.
"We will make maximum effort in the next 10 days or so to break the ice," he said.
The fear is the rivers could overflow because of the ice, and jeopardize the work of the hydro-power plants.
Elsewhere, strong wind knocked over power lines and left tens of thousands without electricity in Bosnia, potentially for the next several days.
Half of the town of Mostar, Bosnia's second largest city, is without power and snow piled some 2 1/2 feet (80 centimeters) is preventing teams from dealing with the problem, government spokesman Pero Pavlovic said.
People in Mostar fell into a "shopping hysteria", emptying shelves and in some cases getting into fist fights over flour, he said.
The Polish Interior Ministry said Wednesday that six more people died as a result of the freezing weather. It also called on people be careful when using coal heaters, reporting that one person died of asphyxiation. The temperatures in the country fell at times to minus 32 C (minus 26 F).
In Bulgaria, the government declared Wednesday a day of mourning for eight people who died after torrential rains and melting snow caused a dam to burst, flooding an entire village. Two people are missing and rescue operations were ongoing.
Dike reinforcement materials and heated tents for flood victims and rescuers have to be supplied, EU commissioner for humanitarian aid Kristalina Georgieva said after visiting the flooded areas. She warned that the freezing weather may be followed by a harsh spring bringing major floods, and people should be prepared for that.
Poland and Italy immediately responded to Bulgaria's request for aid to flood victims, Georgieva said, and added that the Netherlands, Belgium and Denmark also have stated their readiness to help.
The U.S. ambassador to Bulgaria has requested the U.S. Agency for International Development to approve $50,000 in funds for the Bulgarian Red Cross to aid those affected by the flooding.
Aida Cerkez in Sarajevo, Bosnia; Monika Scislowska in Warsaw, Poland; and Jovana Gec in Belgrade, Serbia, contributed to this report.