BELGRADE, Serbia   — Two Russian cargo planes carrying food, generators and rescue boats landed in Serbia on Sunday as part of a relief effort after the worst floods in over a century killed more than 20 people in the Balkan country and neighboring Bosnia.

River levels were still rising in the Serbian capital Belgrade and west towards the Bosnian border, threatening power stations where volunteers joined the army and emergency services in building sandbag barriers.

Tens of thousands of homes were without electricity in Serbia and around 150,000 in Bosnia, where whole swathes of the northeast of the country were under water.

In the worst-hit Serbian town of Obrenovac, waters receded overnight, easing rescue efforts. Authorities say there are fatalities after huge parts of the town, about 18 miles southwest of Belgrade, were submerged under water.

"I carried my kids out on my back, then waited 12 hours to be rescued myself," said 40-year-old Obrenovac resident Dragan Todorovic, who spent the night in a Belgrade sports hall with dozens of other families. "The house was new, built two years ago for 100,000 euros. What now?"

Three people were confirmed dead in Serbia by Friday, following days of the heaviest rainfall since records began almost 120 years ago.

In Bosnia, the death toll reached 19 on Saturday, with nine bodies recovered from the northeastern town of Doboj after what the regional police chief described as a "tsunami" of water 10 to 13-feet deep.

Rescue teams and humanitarian aid, water pumps and generators have arrived from Russia and several European Union member states, including Britain, Germany and Austria, as well as Serbia and Bosnia's fellow former ex-Yugoslav republic Montenegro, Croatia and Slovenia.

Authorities say the economic impact of the floods will be huge, devastating the agricultural sector that is vital to both the Serbian and Bosnian economies.

The Bosnia flooding has also exposed another deadly menace is hiding in the rubble: land mines. Authorities have spent two decades trying to unearth the 1 million land mines planted during Bosnia's 1992-95 war. Before the floods, nearly 120,000 remained in 9,416 marked minefields.

Then floods washed away river banks and fueled landslides that have unearthed minefield warning signs and, in many cases, the unexploded booby traps themselves, the Associated Press reported.

Officials at Bosnia's Mine Action Center say their agency will deploy mine-hunting scouts starting Monday and report that mines already are appearing in unexpected places. They fear that some could float all the way to the Black Sea.