The worst smog in living memory blanketed Moscow Saturday, with residents fleeing the Russian capital or donning protective masks against pollution over six times higher than normal safe levels.
The wildfires which have sparked the smog were still spreading in central Russia with 290 new fires in the last 24 hours as weather forecasters said Russia's worst heatwave in decades would continue for the next days.
Iconic Moscow landmarks including the Kremlin and golden church cupolas disappeared behind a layer of smoke as many Muscovities remaining in the city wore protective masks or simply clutched wet rags to their faces.
Drivers put on their headlights in broad daylight to see through the acrid smog enveloping the capital while the sun appeared as a hazy disc easily viewed by the naked eye with little discomfort.
The smoke -- easily visible from space in NASA images -- penetrated into homes and offices and was even detected inside the Moscow metro, 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 of the League for the Nation's Health group told the Kommersant daily.
Flights from Domodedovo, one of Moscow's main international airports, were disrupted by the smog with flights diverted to other airports. Dozens of flights were delayed and around 40 flights cancelled, state aviation committee Rosavitsia said.
"Visibility around Domodedovo is 325 metres (1,050 feet): it is up to the captain of the aircraft to make a decision about landing," Rosaviatsia official Sergei Izvolsky told Interfax.
The other main international hub, Sheremetyevo in the north of Moscow, was working normally.
Germany closed its embassy until further notice and advised citizens against "non-essential" travel to the affected regions while the US State Department asked nationals to seriously review travel plans.
Russia moved a friendly match with Bulgaria to Saint Petersburg, fearing for the health of the players while Spartak Moscow's home clash with Zenit St Petersburg and the Moscow derby between Dynamo and CSKA were cancelled.
The fires have raised concerns about the security of Russia's main nuclear research centre in the still closed city of Sarov, one of the areas worst hit by the blazes and where the emergencies ministry has sent thousands of workers.
The authorities were also closely watching the situation around the region of Bryansk in western Russia where the soil is still contaminated by the 1986 Chernobyl nuclear disaster.
State air pollution monitoring service Mosekomonitoring said that carbon monoxide levels in the Moscow air were now 6.6 times higher than acceptable levels.
Tiny invisible particles from the fires were also present in concentrations 2.2 times higher than norm, with specialists warning these could prove highly dangerous if they entered the human system.
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, news agencies said.
The situation with the wildfires that have sparked the smog showed no sign of abating, with blazes with an area of 193,500 hectares (478,000 acres) recorded across the country.
In the last 24 hours, 290 new fires were recorded, more than the 244 that were extinguished in the same timespan, the emergencies ministry said. The fires are already confirmed to have killed 52.
Russian President Dmitry Medvedev meanwhile opened a fund to help the victims of the fires, putting in 350,000 rubles (12,000 dollars) of his own money as an initial donation.
Explore further: A model approach for sustainable phosphorus recovery from wastewater