( CNN ) -- Historic flooding in the Balkans sent tens of thousands of people scrambling to higher ground on Sunday and sparked concerns that landmines from the Bosnian war could surface in mudslides , putting rescuers ' lives at risk . `` A vast number of landslides have worsened the situation and relief efforts , '' the Red Cross said , describing the rains as the `` worst floods in more than a century . '' `` There are reports that landmines buried during the conflict and not yet removed are in some instances being shifted with the landslides , adding ( to ) the dangers of people living in the areas as well as rescuers , '' the Red Cross said . In Serbia , the severe flooding has prompted the evacuation of at least 24,300 people . Dragan Radovanovic , president of the Serbian branch of the Red Cross , said the number of people affected by the high water is actually much larger . Many people stayed in the houses or apartments , one rescuer told Reuters . `` Some people simply do not want to leave their homes , '' Novica Biorac , a volunteer from a rafting club in Raska , said . `` We are trying to convince them to leave , but it 's very difficult . '' Water in some places was chest high as rescuers shouted up to people in buildings who are stranded . One woman lowered a bucket , and a worker put a loaf of bread in it . `` Thank you , please come back again and also let us know what the time is . I have a clock but do n't have any batteries , '' she shouted to the rescue team , according to Reuters . Twelve bodies have been recovered in Obrenovac , about 35 kilometers ( 22.7 miles ) from the capital of Belgrade , the Serbian government said Sunday evening . One of the 12 was someone who had already died `` of natural causes , '' Serbian Prime Minister Aleksandar Vucic said , according to a government statement . Authorities estimate that 90 % of the town has been flooded . At least 13 people are dead in Bosnia and Herzegovina , Deputy Minister of Security Samir Agic said . The toll is likely to go even higher , officials cautioned . One of the deceased was a rescuer , Radovanovic said , though he said he knew of five deaths in Serbia . It 's the worst flooding Serbia has seen since the country began keeping records 120 years ago , according to meteorologists . `` Many cities and villages in western Serbia are completely under water , '' the Serbian Embassy in Washington said in a statement Sunday , describing the situation as `` critical '' and an `` unimaginable catastrophe . '' Volunteers , soldiers and rescue workers have stacked sandbags in towns near rivers throughout the country , the statement said . The catastrophic weather has prompted authorities to declare a state of emergency in neighboring Bosnia and Herzegovina , according to a government statement . Bosnian authorities say the flooded town of Maglaj received the average rainfall for two months in less than two days . The Prime Minister pointed out that a dam 7.3 meters tall ( 24 feet ) has been erected , but that the current level of the Sava River is over 6.3 meters -- a historic high . The river is expected to rise near Belgrade . He warned that it is difficult to predict what will happen if the river reaches 6.8 meters , or slightly more than 22 feet . In Kostolac , along the Danube River , workers were building sandbag walls to protect the thermal power plant there , one the energy minister called the most important power facility in Serbia . A written statement said it produces 20 % of the nation 's power . The Prime Minister thanked the many countries that have already come to Serbia 's aid . He was especially grateful to members of the Russian special forces , highlighting one member who swam 200 meters ( 656 feet ) in cold water to save several people . Russia and Israel each announced Sunday they would send relief supplies . According to Finance Minister Dusan Vujovic , more than 10,000 troops have already been involved in rescue and assistance operations . CNN 's Jo Shelley and Radina Gigova contributed to this report .
NEW : Bosnia and Herzegovina : `` Many cities and villages ... are completely under water '' more than 10,000 people dead in Serbia , government says . It 's the worst flooding Serbia , part of the Balkans Peninsula , has seen in two months . the Red Cross says surfacing landmines could endanger rescuers and residents .