The ministry had also reported sporadic wildfires last week, but said all were put out.

Irina Yegorushkina, the ministry spokeswoman, said on Wednesday that radiation experts from Moscow determined there has been no increase in radiation levels in the Bryansk area, located on the border of Belarus and Ukraine.

The forest floor holds radioactive particles that settled after the Chernobyl disaster, which environmentalists warned could be thrown into the air by the fires raging across western and central Russia.

"A cloud may come up in the air with soot and spread over a huge territory," Alexander Isayev of the Moscow-based Center for Forest Ecology and Productivity, told the Associated Press.

Neave Barker, Al Jazeera's correspondent in Moscow, said: "There have been a number of really serious concerns regarding the potential for radioactive smoke.

"Huge swathes of land, following the Chernobyl disaster, were contaminated with radiation.

"The fear here is that fires on these territories could send plumes of radioactive smoke billowing in the direction of built-up areas."

Radioactive elements

The most dangerous radioactive elements left by the Chernobyl accident are cesium and strontium, which with repeated exposure could raise the risks of cancers and genetic disorders.

Hundreds of wildfires sparked by the hottest summer ever recorded in Russia have engulfed large areas of the country's west.

The mortality rate in Moscow has doubled recently as wildfires blanketed the capital with toxic smoke.

Morgues have been overflowing, and residents have been desperately seeking ways to stay cool amid soaring temperatures and air pollution.

About 165,000 workers and 39 firefighting aircraft were battling more than 600 blazes nationwide on Wednesday over 220,000 acres, according to the Emergency Situations Ministry.