Water levels have started falling in several countries, but Romania, the worst-hit, is still battling cracks in strained flood defences in the Danube delta near the Black Sea and faces the risk of further flooding and evacuations.

"The water flow is expected to remain high over the next 35 days and this is a permanent threat to defences and people," Environment Minister Sulfina Barbu told state radio.

Lefter Chirica, the government's representative in the county of Tulcea, told Reuters: "580 people fled overnight from the village of Ostrov in the delta as high waters threatened their lives after several dikes collapsed."

Flooding caused by heavy rain and melting snow has forced thousands of people living on the Danube's flood plains out of their homes over the past month, including around 15,800 in Romania where about 130,000 hectares of farmland and pastures are submerged.

Preliminary estimates show the Danube has inundated 59,000 hectares of farmland in Romania, a major grains producer. Another 69,000 hectares were submerged in controlled flooding operations.

But authorities say damage to farming so far in the Balkans is far smaller than the losses that followed last year's flooding in the region.

In Bulgaria, soldiers stacked sandbags in some areas but dikes have held up and no new evacuations were ordered.

The Danube has flooded 7,500 hectares of wheat throughout Bulgaria, less than one percent of the planted area, farm officials said, but added high waters were preventing detailed damage estimates.

"Our first job is to start disinfection in the affected areas," said Elena Yaneva, spokeswoman of the disaster management ministry.