Russian planes seeded clouds to bring rain on huge bushfires raging in the Siberian region of Yakutia, authorities said on Monday.
In one place, the flames spread dangerously close to a hydroelectric power plant, they said.
Fires have flared across Russia amid a heatwave, tearing through more than 1.5 million hectares of land in Yakutia, the worst-hit region.
On Sunday, officials told people to stay indoors and keep windows shut because of the smoke.
The regional capital Yakutsk, sometimes called the planet's coldest city, was forced to suspend flights because of bad visibility, and transport on the river Lena that winds through Siberia was also interrupted.
Fires flare across Russian forest land every year but they have become more intense recently amid unusually high temperatures across the northern Siberian tundra. Yakutia is in the grips of a heatwave.
In less than two months, fires in the region have emitted about 150 megatonnes of carbon dioxide equivalent, close to the 2017 annual fossil fuel emissions of Venezuela, says the Copernicus Atmosphere Monitoring Service, part of an EU programme.
On Monday, a Beriev Be-200 amphibious plane flown in from another Siberian region joined a massive effort to contain a blaze involving more than 2,000 firefighters.
About 123 fires raged on Monday over an area of more than 885,000 hectares, the region's Environment and Forest Ministry said.
Firefighters took special care to contain one fire covering 41,300ha, the ministry said.
"There's a natural water barrier from the river Vilyuy but the fire is potentially dangerous for the ... Svetlinskaya hydroelectric power station," it said.
Smaller-scale fires burned in less remote parts of the country as more than 6,500 firefighters fought to contain them.
In Karelia, a region that borders Finland, authorities moved more than 600 villagers to safety, the Tass news agency reported.