Torrential rain caused devastating flash floods in southern Russia, claiming 150 lives so far.

The death toll is likely to increase as scores are still missing in one of the worst floods to hit the region in decades.

Russian President Vladimir Putin surveyed the battered Krasnodar region from a helicopter and ordered extensive relief measures, including the allocation of special funds to build new homes for those affected.

"I have asked the leadership of the (federal) Investigative committee to come down. The investigative committee will check the actions of all the authorities - how the notice was given, how it could have been given, how it should have been given and who acted how," the Itar-Tass news agency quoted Putin as saying, according Reuters.

Two months' worth of rain fell overnight, wreaking havoc in the region.

Most of those who perished were taken by surprise and drowned in their sleep. Police said a large number of them were elderly.

Houses in Krymsk and other nearby towns were completely submerged by the flood water.

Authorities have rescued 6,000 survivors, who climbed on to trees and rooftops to escape the rising water. More than 10,000 residents are estimated to have been affected by the flooding.

"Our house was flooded to the ceiling. We broke the window to climb out. I put my five-year-old grandson on the roof of our submerged car and then we somehow climbed up into the attic," Krymsk pensioner Lidiya Polinina told AFP.

Seven-metre waves were reported to have hit the town, with some witnesses describing it as a tsunami.

Power, communication and roads have been disrupted by the flooding, hampering rescue work.

Resident wades through flooded street in village of Novoukrainsk, near southern Russian town of KrymskReuters
Car stranded in deluge in southern Russian town of KrymskReuters
Resident carries child through flooded street in KrymskReuters
Resident returns with provisionsReuters
Man wipes brow in village of NovoukrainskReuters
Car lies submerged in flooded street in NovoukrainskReuters
Residents survey damage in KrymskReuters
Woman in Krymsk gestures about devastating effects of floodingReuters