Serbian authorities have ordered the urgent evacuation of 12 villages and towns along the raging Sava River, including one where soldiers, police and volunteers have been working around the clock to protect Serbia's main power plant.
The coal-fired Nikola Tesla power plant, which supplies electricity for half of Serbia and most of Belgrade, lies in the flood-hit town of Obrenovac, 20 kilometres (16 miles) upstream of the capital. Emergency crews have so far defended the power plant by building high walls of sandbags but it's not clear those will withstand the force of an upcoming river surge.
Serbian police chief Nebojsa Stefanovic ordered the town completely evacuated of civilians, along with 11 villages along the Sava. Some 300 people were evacuated from Obrenovac by helicopter on Monday, authorities said.
Serbia and Bosnia are struggling with the worst flooding in southeastern Europe in more than a century. At least 35 people have died in five days of flooding caused by unprecedented torrential rain. Entire towns and villages are underwater, thousands of hills have crumpled into landslides and tens of thousands have been forced to flee their homes.
The death toll is expected to rise further as floodwaters recede after the worst rainfall in 120 years of records.
The situation in Obrenovac was critical on Monday, said Predrag Maric, a Serbian emergency official. The Sava flood wave was expected to begin to reach Obrenovac and Belgrade later on Monday and peak by Wednesday.
Before Monday's order, some 7800 people were already evacuated from the town, where many homes were submerged. But some 2000 people were still believed trapped in the higher floors of buildings there, without power or phone lines.
In Bosnia, Foreign Minister Zlatko Lagumdzija called the flood damage "immense" and compared it to the carnage during the country's 1992-95 war that killed at least 100,000 people and left millions homeless. He said the flooding had destroyed about 100,000 houses and 230 schools and hospitals and left a million people without drinking water.
"The only difference from the war is that less people have died," he said. "The country is devastated ... this is something that no war in the history of this country" ever accomplished.
In Orasje, a Bosnian border town, frantic efforts were being made to prevent the Sava further surging through broken barriers. Ideas included dropping old trucks from helicopters or covering the gaps with wire frames and then reinforcing with sandbags.
The emergency commander in the town, Fahrudin Solak, said the decaying corpses of drowned farm animals now represented a major health risk.
"We are sending out mobile incinerators and we have asked for international assistance, to send us more incinerators to prevent diseases," he said.
Floods have also triggered more than 3000 landslides across the Balkans. Aside from sweeping away home and barns, the landslides have carried land mines left over from the region's war, along with their warning signs, to entirely new, often unknown, locations.
"Landslides and land mines devastated very fertile land," Lagumdzija said.