Russia is observing a day of mourning for the victims of the flash floods in southern Krasnodar region, - BBC reported.

At least 171 people were killed in the disaster, officials said on Sunday.

President Vladimir Putin has ordered an enquiry into whether people were given enough warning of the disaster. A separate criminal investigation is under way into possible negligence.

Officials deny allegations blaming the ferocity of the floods on the opening of reservoir sluice gates.

The day of mourning and enquiry were called by Mr Putin after he toured the affected area in a helicopter on Saturday.

It was the first major disaster in Russia since Mr Putin, 59, returned for a third-term earlier this year, after a four-year term as prime minister.

The flash floods, the worst in living memory in the region, struck in the Krasnodar region on Friday night, after days of torrential rain. People were reportedly given little or no warning.

The rains dumped as much as 28cm (11 inches) of water overnight, forcing many residents to take refuge in trees or on house roofs.

TV pictures later showed thousands of houses almost completely submerged with people scrambling onto their rooftops to escape the rising waters.

Most of those who died were in and around Krymsk, a town of 57,000 people. But deaths were also reported in the Black Sea resort of Gelendzhik and in the port town of Novorossiysk.

Krasnodar governor Alexander Tkachev said on Sunday that more than 24,000 people had been affected by the floods, according to Russian media reports. The regional authorities say more than 5,000 houses were inundated.

"It's an unprecedented tragedy. There has been nothing like it in our history," Mr Tkachev said.