The Canadian and Polish embassies have started evacuating their family members from Moscow as thick smoke from wildfires blanketed almost the entire city.
The embassies started the evacuation on Friday after Russia's Surgeon General advised those who can to leave the city, Xinhua reported citing the Business Special Report Russia magazine.
A top environment agency in Moscow said the air quality was so bad that "walking outside without a mask is equivalent to smoking two packets of cigarettes a day".
"Air quality has been deteriorating, conditions unfavourable for atmospheric dispersion," the Moscow Nature Utilisation and Environmental Protection Department said.
The situation could get worse as fires broke out in Bryansk, some 350 km southwest of Moscow on the Ukrainian border, which was earlier affected by the Chernobyl nuclear disaster in 1986.
Sergei Shoigu, head of the emergency ministry, warned on Friday that if fires spread in the region, they could lift radioactive elements that exist in the soil into the air and contaminate other regions.