* Worst flooding in Balkans in over a century
* Death toll in Bosnia reaches eleven
* Volunteers rush to defend west Serbian town
By Marko Djurica
OBRENOVAC, Serbia, May 17 (Reuters) - Emergency services pulled seven dead bodies from flooded homes in Bosnia on Saturday and soldiers rushed to free hundreds of people stranded in a school in Serbia during the worst floods to hit the Balkans in over a century.
A Reuters photographer in the town of Obrenovac, 30 km (18 miles) southwest of the Serbian capital Belgrade and the worst hit by days of heavy rainfall, estimated the water level at 2-3 metres.
"The whole town is under water," he said.
Residents stood on roofs and terraces waiting to be rescued, while soldiers in amphibious military vehicles tried to evacuate an estimated 700 people, mainly women and children, from a primary school located on higher ground.
Further to the west, thousands of volunteers joined soldiers, police and firefighters overnight in building sandbag flood defences around the town of Sabac, threatened by the rising waters of the River Sava.
"Now we have to sit and wait, to wait for that next wave and to hope," Serbian Prime Minister Aleksandar Vucic told a news conference.
Vucic said the first bodies had been found in Obrenovac, worst hit by the heaviest rainfall in the region since records began almost 120 years ago. He did not specify how many people had died.
In Serbia, some 95,000 homes were without electricity on Saturday, with the country's energy system near breaking point. The country hiked imports to make up for a cut of 40 percent in capacity.
By Friday in Serbia, three people had drowned, including a rescue worker. In Bosnia, the death toll reached 11, with the discovery of six bodies in the eastern town of Doboj on Saturday and another in Samac in the north.
"I'm afraid that won't be the end," Bosnian Serb leader Milorad Dodik told a news conference with Vucic in Belgrade.
Authorities in Bosnia said they would evacuate about 10,000 people from the eastern region of Bijeljina, accomodating them in schools. Mayor Mico Micic appealed for blankets and food.
Helicopters evacuated people from the northern Bosnian towns of Samac and Modrica and trucks and bulldozers carried food to the hardest hit areas.
About 1,000 people, including babies, pregnant women, invalids and elderly were evacuated from the region of Zeljezno Polje in central Bosnia, where hundreds of homes were destroyed in landslides.
"I think we'll never be able to return to our village," local Muslim imam Zuhdija Ridzal told Reuters by telephone from Zeljezno Polje. "It has disappeared in landslides."
Serbia's state-run power utility Elektroprivreda Srbije (EPS) trimmed output at its largest hydro power plant, Djerdap 1, on the Danube river by a quarter and closed down 1,650 MW in capacity of its largest coal-fired power plant Nikola Tesla (TENT) late on Friday, on top of a 10 percent cut in total output a day before.
Flooding of the Kolubara, the Danube and the Sava rivers brought down cables and transformer stations, soaked coal depots that feed power plant and caused a fire inside the Kolubara power plant complex which had been shuttered since Thursday. (Additional reporting by Daria Sito-Sucic and Maja Zuvela in Sarajevo, Fedja Grulovic in Belgrade; Writing by Matt Robinson; Editing by Angus MacSwan)