Kazakhstan has declared a national disaster and diverted funding for relief efforts, evacuating well over 100,000 people and saying 16,000 tons of oil production had been lost so far. Aerial videos have shown vast areas under water, with some homes submerged up to their rooftops.

Workers and volunteers in the cities of Oral and Atyrau were building dams and barriers to protect residential, agricultural and industrial areas from water.

The energy ministry said walls 2 to 2.5 meters (6'7 to 8'2) tall have been built around the Atyrau oil refinery which is close to the river, although the authorities still appeared not to rule out possible disruptions to its work. Sufficient fuel stocks had been created across the country, officials said.

In Russia, the governor of the Tyumen region, a centre of oil and gas production, said on Wednesday up to 100 settlements were expected to be flooded in coming days as he discussed the flooding with President Vladimir Putin in a televised meeting.

Water levels have continued to rise in the Tobol and Ob rivers in Russia's Kurgan and Tomsk regions respectively, local authorities said on Thursday.

In the city of Kurgan, the Tobol had risen to 9.77 m (32 ft) as of Thursday, the regional administration said, urging people to evacuate areas threatened by floods.

In the Tyumen region in Siberia, crossed by the Tobol and Ishim rivers, more than 1,500 people have been evacuated, Russia's emergencies ministry said. In the worst case scenario, floods could threaten 94 towns and villages with a total population of 31,000 people, it said.

The Interfax news agency cited the government of the Tomsk region as saying that water levels in the Ob river were above dangerous marks in parts of the region, but were subsiding in its tributary river, the Tom.

The disaster has been caused by the unusually fast melting of large snowfalls amid heavy rain, swelling the tributaries of several of Europe's largest rivers.

A senior Putin ally said this week that regional authorities had fallen short in their forecasting and emergency response.

(Reporting by Tamara Vaal; Writing by Olzhas Auyezov; Editing by Philippa Fletcher)