Authorities in the Russian city of Orenburg called on thousands of residents to evacuate immediately on Friday due to rapidly rising flood waters after major rivers burst their banks due to a historic deluge of melting snow.
Water was also rising sharply in another Russian region - Kurgan - and in neighboring Kazakhstan the authorities said 100,000 people had been evacuated so far, as rapidly warming temperatures melted heavy snow and ice.
The deluge of melt water has forced over 120,000 people from their homes in Russia's Ural Mountains, Siberia and Kazakhstan as major rivers such as the Ural, which flows through Kazakhstan into the Caspian, overwhelmed embankments.
Regional authorities called for the mass evacuation of parts of Orenburg, a city of over half a million people about 1,200 km (750 miles) east of Moscow.
"There's a siren going off in the city. This is not a drill. There's a mass evacuation in progress!" Sergei Salmin, the city's mayor, said on the Telegram messenger app.
Emergency workers said water levels in the Ural river were more than 2 meters (6.5 ft) above what they regarded as a dangerous level. Water lapped at the windows of brick and timber houses in the city, and pet dogs perched on rooftops.
Salmin called on residents to gather their documents, medicine and essential items and to abandon their homes.
People living in flooded homes lamented the loss of their belongings.
"Judging by the water levels, all the furniture, some household appliances and interior decorating materials are ruined," local resident Vyacheslav told Reuters as he sat in an idling motorboat and gazed over his shoulder at his two-storey brick home, partially submerged in muddy water.
"It's a colossal amount of money."
Alexei Kudinov, Orenburg's deputy mayor, had said earlier that over 360 houses and nearly 1,000 plots of land had been flooded overnight. He said the deluge was expected to reach its peak on Friday and start subsiding in two days' time.
Orenburg Governor Denis Pasler told President Vladimir Putin on Thursday that 11,972 homes had been flooded and if waters rose further 19,412 more people would be in danger.
The village of Kaminskoye in the Kurgan region was also being evacuated on Friday morning after the water level there rose 1.4 metres overnight, Kurgan's regional governor Vadim Shumkov said on the Telegram messaging app.
Kaminskoye is a settlement along the Tobol river which also flows through the regional center Kurgan, a city of 300,000 people. Shumkov said a deluge could reach Kurgan in the coming days.
"We can only hope the floodplain stretches wide and the ground absorbs as much water as possible in its way," he said, adding that a dam was being reinforced in Kurgan.
Kurgan is home to a key part of Russia's military-industrial complex - a giant factory that produces infantry fighting vehicles for the army which are in high demand in Ukraine where the Russian military is on the offensive in some areas.
There were no reports that the factory, Kurganmashzavod, had so far been affected.
Rising water levels are also threatening southern parts of Western Siberia, the largest hydrocarbon basin in the world, and in areas near the Volga, Europe's biggest river.
Water levels in some other Russian regions are expected to peak within the next two weeks.
