Firefighters are battling wildfires covering 1700 square kilometres, as the country swelters in a heatwave.
The head of the Moscow's health department, Andrei Seltsovsky, said on Monday that deaths had almost doubled to 700 daily, with heat being the main killer.
The Health Ministry criticised Mr Seltsovsky, saying it was "bewildered by these unofficial figures" and that Moscow's death rates had actually fallen in January-June.
Officials say 52 people have been directly killed by the fires that have ravaged forests and fields and destroyed some villages since last month.
Wheat harvest warning
Russia's worst drought in decades has also affected world grain markets, driving up wheat prices.
Prime Minister Vladimir Putin issued a further warning over shortfalls in Russia's grain supply, saying this year's harvest, hit by fire and drought, would be worse than previously forecast.
Mr Putin said the harvest could be as low as 60 million tonnes, rather than the current forecast of 65 million tonnes, the BBC reported.