Russia and Kazakhstan ordered more than 100,000 people to evacuate after swiftly melting snow swelled mighty rivers beyond bursting point in the worst flooding in the area for at least 70 years.

The deluge of meltwater overwhelmed scores of settlements in the Ural Mountains, Siberia and areas of Kazakhstan close to rivers such as the Ural and Tobol, which local officials said had risen by meters in a matter of hours to the highest levels ever recorded.

Late on Tuesday, levels of the Ural River in Orenburg, a city of around 550,000, reached 9.31 meters (30.5 feet), exceeding the critical level of 9.30 meters, a regional governor said, urging residents in areas at risk to evacuate.

"I am calling for caution and for those in flooded districts to evacuate promptly," Denis Pasler, the governor of Orenburg said on Telegram.

City residents paddled along roads as though they were rivers. Dams and embankments were being reinforced.

Upstream on the Ural, floodwaters burst through an embankment dam in the city of Orsk last Friday.

Regional officials said water levels in Orsk had subsided by 21 centimetres (8.27 inches) and now stood at 9.07 meters—still well over the official danger level of about 7 meters. Russia's Emergencies Ministry said water levels had declined in some areas but described the situation as "still difficult."

The Ural is Europe's third longest river, which flows through Russia and Kazakhstan into the Caspian.