Health authorities in Russia have urged residents of Moscow to stay indoors because of pollution from forest fires.
Those people that have ventured out are wearing sanitary masks or clutching wet rags to their faces.
The fires have left at least 52 people dead and damaged vast areas of forestry across seven regions.
Experts have warned that the concentration of toxic particles is up to five times higher than safe levels.
Many of the city's iconic landmarks, such as the Kremlin and golden church cupolas, have disappeared behind a layer of smoke.
Drivers have put on their headlights in broad daylight to see through the acrid smog that has descended on the capital.
The smoke has penetrated into homes and offices and is even visible inside the Moscow metro, which is one of the deepest underground systems in the world.
'The situation is truly extreme. People are in circumstances under which they should not have to live,' leading Russian doctor Ivan Yurlov told the Kommersant daily newspaper.
Flights from Domodedovo, one of Moscow's main international airports, have been disrupted by the smog.
Several flights were diverted to other airports and around 40 flights have been cancelled, state aviation committee Rosavitsia said.
'Visibility around Domodedovo is 325 metres: it is up to the captain of the aircraft to make a decision about landing,' said Rosaviatsia official Sergei Izvolsky.
With health experts warning that the best solution was to leave the city for the weekend, package tours abroad were completely sold out and there was a rush for seats on trains and planes out of the capital.
The situation with the wildfires that have sparked the smog shows no sign of abating, with blazes with an area of 193,500 hectares recorded across the country.
The emergencies ministry said that 290 new fires have been recorded in the last 24 hours.
