PETROPAVLOVSK, Kazakhstan - Swathes of northern Kazakhstan and Russia's Urals region were flooded on Monday as melt waters swelled the tributaries of the world's seventh longest river system, forcing more than 125,000 people to flee their homes.

Russia's southern Ural region and northern Kazakhstan have been grappling with the worst flooding in living memory after very large snow falls melted swiftly amid heavy rain over land already waterlogged before winter.

That has swelled the tributaries of the Ob, which rises in the Altai Mountains of southern Siberia and empties into the Arctic Ocean, beyond bursting point, leaving some cities in Russia and Kazakhstan under water.

A Reuters journalist said several districts of the northern Kazakh city of Petropavlovsk were completely flooded. The city which sits on the Ishim River, a tributary of the Irtysh, the chief tributary of the Ob.

Almost 1,000 houses have been flooded in the North Kazakhstan region of which Petropavlovsk is the centre, and over 5,000 people have been evacuated, local officials said. There have been interruptions in power and water supply in the city.

People were queuing up in front of water trucks moving from one neighbourhood to another in the city. The main reservoir supplying the city with drinkable water has been flooded.

Just a few hundred kilometres over the border, Russia's Kurgan, a region of 800,000 people at the confluence of the Ural mountains and Siberia, was grappling with flooding and rising water levels in the Tobol River, another tributary of the Irtysh.

Water levels rose to 6.31 metres (over 20 ft) in the main city, Kurgan. Governor Vadim Shumkov said the main mass of water was 10 km away from the city.

"The volume of water is colossal," Shumkov said. "In addition to the waters of the Tobol itself and melt water pouring into it, there is 1.3 billion cubic metres of water coming from Kazakhstan, which... is twice as much as in 1994 (when Kurgan was flooded for a month)."

"Fellow countrymen, leave the flooded areas immediately."

Shumkov warned that flooding would begin shortly on the right bank of the Tobol, which slices the region south to north, and the low part of its left bank.

Floods were also inundating homes in the Tomsk region in the southwestern part of Siberia, regional officials said on Telegram.

Almost 140 houses near the city of Tomsk, which is the regional administrative centre, were under water on Monday and 84 people were evacuated.

The Ob-Irtysh river system is the world's seventh largest, after the Yellow River, the Yenisei, the Mississippi, the Yangtze, the Amazon and the Nile.

Kazakhstan was also evacuating settlements in its West Kazakhstan region, expecting fresh inflows of water in the Ural river in the coming days. REUTERS