Floods in Russia's Urals force thousands to evacuate

Floodwaters are rising in two cities in Russia's Ural mountains after Europe's third-longest river burst through a dam, flooding at least 10,000 homes and forcing thousands of people to flee with just their pets and a few belongings.

Some of the worst floods in decades have hit a string of Russian regions in the Ural Mountains and Siberia, alongside parts of neighbouring Kazakhstan in recent days.

The Ural River, which rises in the Ural Mountains and flows into the Caspian Sea, swelled several metres in just hours on Friday due to melt water, bursting through a dam embankment in the city of Orsk, 1800km east of Moscow.

More than 6100 people were evacuated in Orsk as swathes of the city of 230,000 were flooded. Footage published by the Emergencies Ministry showed people wading through neck-high waters, rescuing stranded dogs and travelling along flooded roads in boats and canoes.

State news agency TASS reported that six adults and three children had been hospitalised in Orsk, but their condition was not life-threatening.

President Vladimir Putin ordered Emergencies Minister Alexander Kurenkov to fly to the region. The Kremlin said flooding was now also inevitable in the Urals region of Kurgan and the Siberian region of Tyumen.

Putin had spoken to the governors of the regions by telephone, the Kremlin said.

In Kurgan city, which has a population of 310,000, authorities ordered residents of one riverside neighbourhood to evacuate urgently, saying floodwaters would soon arrive in the city.

The Orenburg region's governor, Denis Pasler, said the floods were the worst to hit the region since records began.

He said flooding had been recorded along the entire course of the 2400km Ural River, which flows through Orenburg region and then through Kazakhstan into the Caspian Sea.

Russian media cited Orenburg region authorities as estimating the cost of flood damage locally as around 21 billion roubles ($A345 million) and saying floodwaters would dissipate only after April 20.

In Kazakhstan, President Kassym-Jomart Tokayev said on Saturday the floods were his country's largest natural disaster in terms of scale and impact for 80 years.

North Korea leader Kim Jong-un expressed sympathy to Putin about the flood, state media KCNA said, underscoring stronger ties between Moscow and Pyongyang after the leaders met last year.

"Our people will always be with the Russian people," Kim said.

Flood warnings were issued in other Russian regions and Kurenkov said the situation could get worse very fast.

"The water is coming, and in the coming days its level will only rise," said Sergei Salmin, the mayor of Orenburg, a city of at least 550,000 people. "The flood situation remains critical."

Emergencies Minister Kurenkov said bottled water and mobile treatment plants were needed, while local health officials said vaccinations against Hepatitis A were being conducted in flooded areas.

Local officials said the dam in Orsk was built for a water level of 5.5 metres yet the Ural River rose to 9.6 metres.

Federal investigators opened a criminal case for negligence and the violation of safety rules over the construction of the 2010 dam, which prosecutors said had not been maintained properly.