Ice floes up to one metre (three feet) thick smashed into hundreds of boats on the River Danube near Belgrade as a thaw set in, sinking a floating restaurant, officials and witnesses said Monday.

Barges also broke adrift under the pressure of the ice as it melted and broke up following a rise in temperature at the end of a two-week cold snap that killed hundreds of people across Europe.

"Hundreds of small boats were damaged or sunk, while almost 90 percent of rafts were moved up to 20 metres (yards) downstream," Zoran Matic of the Belgrade water company told AFP.

Three ice-breakers had been brought in to reduce the pressure on rafts "in order to save what could be saved," Matic said, adding that at least one raft-restaurant sank.

"The damage is enormous. This is a disaster," a desperate boat owner told a local radio.

During the cold snap, which brought temperatures well below freezing for days on end, the 2,860-kilometre (1,780-mile) Danube, which flows through 10 countries and is vital for transport, power, irrigation, industry and fishing, was nearly wholly blocked by ice, from Austria to its mouth on the Black Sea.