Soldiers with face masks hose water onto smouldering embers in a forest in the Noginsk district, some 70 kilometres east of Moscow, on Tuesday. (Misha Japaridze/Associated Press)

Wildfires have been spotted in areas of Russia that were severely contaminated by radiation from the Chornobyl reactor explosion in 1986 — raising fears that smoke could spread the radiation further.

Six wildfires have been put out this week in the Bryansk region, the area of Russia most affected by the nuclear disaster.

When the Chornobyl Unit 4 reactor exploded 24 years ago, it spewed radioactive particles over a large part of northern Europe and what was then the western Soviet Union.

Those particles settled into the soil, where they remain today.

Environmentalists have warned there is a danger that fires and winds could carry radiation far outside the contaminated area, although it would be at far lower levels than around Chornobyl.

Russian emergency workers have boosted their patrols around the Bryansk region. So far, no increase in radiation levels has been detected.

"There is a danger, but we are controlling the situation," said Vladimir Rozinkevich, chief of the forest protection service in the Bryansk area.

Moscow misery

Russia's Emergency Situations minister has addressed the danger, but said the threat around Moscow was more serious.

Dozens of wildfires raging near the capital have made life miserable for millions of Muscovites.

While a shift in the wind cleared the skies over Moscow on Wednesday, choking smog and temperatures approaching 40 C have left Moscow's residents gasping for breath for more than a week.

As many as 700 deaths a day are being reported in the city — twice the normal number.

More than 600 fires are burning across Russia, covering more than 90,000 hectares.

The heat wave, which is expected to last another 10 days, has caused widespread destruction of crops and led to a ban of grain exports.

With files from The Associated Press