A new flood wave from the River Sava is threatening Serbia's largest power plant, the Nikola Tesla complex - which provides half of the country's electricity.

Workers at the power facility worked through the night to build barricades of sandbags to prevent floodwater from breaching the complex, according to union spokeswoman Djina Trisovic.

"The plant should be safe now," she told Reuters. "We've done all we could. Now it's in the hands of God."

Meanwhile the Balkan flooding death toll has risen to 39. Between the Bosnian cities of Zenica and Zpece, entire villages have been swalled by earth, as have settlements between Topcic Polje and Zeljezno Polje, according to rights group Society of Threatened Peoples.

"The consequences ... are terrifying," Bosnian Foreign Minister Zlatko Lagumdzija told a news conference.

"The physical destruction is not less than the destruction caused by the war," he added, comparing the devastation to the 1992-95 Bosnian War.

"During the war, many people lost everything," he said. "Today, again they have nothing."

Lagumdzija continued to detail the effect of the flooding, revealing that more than 100,000 properties and buildings were no longer fit to use within Bosnia, and that over 1 million people cannot access clean water.

Bosnia has said that a quarter of its four million population have been affected by the worst floods to hit the country since records began, after rivers overflowed causing numerous landslides across the region.

"We have some indications that a half a million Bosnians have either been evacuated or have left their homes because of flooding or landslides," said Fahrudin Solak, the head of Bosnia's civil defence service.

Displacement of this magnitude has not been witnessed in the region since ethnic cleansing caused over a million to flee during the Bosnian War.

Another concern for the Bosnian people are the 120,000 unexploded land mines which remain in over 9,400 minefields.

The floods have removed warning signs and dislodged the mines, posing the risk that mines could be transported around southeastern Europe.