"Around 30 percent of the displaced people have no place to go and are staying in schools and in camps we had created for them ... They won't have a place to return to after waters recede," an interior ministry official told Reuters.

"Our efforts are now concentrated to prevent water-borne diseases," he said.

Flooding risk from the Danube has gradually subsided over the past days but officials said many waterlogged dikes could still give way because of the prolonged water pressure.

The Danube poured over dams and burst defences throughout central and southeastern Europe this month as melting snow and heavy rains raised water levels to century highs.

Health authorities in Romania have been distributing anti-dysentery tablets to the evacuees and vaccinated them against tetanus and water-borne diseases such as typhoid.

TV footage has shown military helicopters spraying disinfectants and anti-mosquito insecticides onto villages over a 1,000-km (620 mile) stretch of the river to prevent malaria threat.

But the effort may not be enough, officials say.

"The longer our 1,200 people stay in tents, the shorter the way to an epidemics," Iulian Silisteanu, mayor of the worst hit village of Rast in southwestern Romania told Reuters.

"I've lost hope," says Ion Bita, a 52-year-old farmer from the village of Rast who has spent two weeks in a tent pitched on higher ground.

In Bulgaria, civil defence units are working on draining and disinfecting flooded houses and land along the Danube, officials said.

A team of experts from Belgium is due to arrive on Sunday to help pump out water in the worst hit town of Nikopol, where more than 80 houses and public buildings are still under water.

Upstream from Romania, in Hungary, about 1,000 people returned to their homes on Sunday, reducing the number of evacuees to 1,642 from 2,645.