A man wades in a fountain outside the Kremlin in Moscow on Friday to escape the heat. (Sergey Ponomarev/Associated Press)

Fish breeders in central Russia have lost much of their sturgeon and trout to a scorching heat wave that continued Saturday.

At Volgorechensk fish farm, near the Volga River, farmers say they have been forced to throw away 12 tonnes of fish because of high temperatures.

"The big fish of six, seven, eight years old suffer and die the most. Little fish handle the heat better, but the big ones … you see what's happening," said chief fish breeder at the farm, Irina Tikhomirova.

Specialists at the fish farm were trying to rescue the remaining fish by transferring them from the farm tanks to cages in the river, where the water is cooler.

A state of emergency has been declared in 19 Russian regions due to the worst heat wave since the Stalin era.

Saturday could see temperatures in Moscow hit 37 C, which would break the previous high of 36.6 C set in 1936. The state weather bureau in Moscow said it expected the heat wave to continue into next week.

Russia is facing its worst drought in 130 years, with little or no rain for weeks across several regions. On Thursday, officials reported that dry conditions have destroyed nearly 10 million hectares of crops.

With files from The Associated Press