Due to widespread forest fires, a state of emergency was declared on Monday in the Russian region of Ryazan, some 200 kilometres southeast of Moscow.
Russian agencies reported that the fires covered an area of about 9,000 hectares, citing aerial observations by the Forestry Agency.
Acrid smoke has reached Moscow in recent days, limiting visibility there.
Moscow Mayor Sergei Sobyanin reportedly sent 9,000 relief workers with more than 2,300 vehicles and heavy equipment from the capital to the fire-hit region to support local forces.
Firefighting aircraft and helicopters were also deployed.
Meteorologists predicted that the smoke will remain noticeable in Moscow until the end of the working week.
The Russian capital also expects a heat of 30 to 33 degrees Celsius.