Flash floods brought the Black Sea resort of Sochi to a standstill on Thursday, halting trains and leaving cars half-submerged in the city where Russia staged the Winter Olympics.
State-run Russia Today television said troops had been sent to evacuate people from some areas outside Sochi after several hours of torrential rain. The report could not immediately be confirmed.
Russian Railways said trains had been halted to the station in Adler, the district that hosted many of the Olympic events, and that it had set up a crisis center to help cope with the flooding.
There was no word of any casualties.
A Reuters cameraman said some roads were impassable and people were trying to retrieve parked cars that had been left almost completely under water. Others were clearing flooded cellars and courtyards where the water was knee-high.
Russia Today said the Formula One race track at Adler was also hit by the flooding.
"There's no water, no gas, no electricity. They say it could be back tonight or maybe tomorrow," said Alla Atakyan, a resident of Adler.
Rain also affected other areas of southern Russia, including the Krasnodar wheat producing and exporting region which started harvesting a few days ago.
"The situation is difficult but the rain should stop in two or three days and dry weather is expected next week," said Dmitry Rylko, head of the IKAR agriculture consultancy.
"There is a possibility that wheat quality will be damaged in some areas but we do not expect any disastrous consequences," he said.
Further south, in the former Soviet republic of Georgia, severe flooding last week killed at least 19 people in the capital Tbilisi and caused extensive damage. Dozens of animals escaped from Tbilisi zoo, including a tiger which killed a man before being shot dead.