Dozens of commercial planes are being diverted from Moscow airports as peat and forest fires blanket the capital in smoke.
Russia's aviation authority said at least 60 planes had been diverted from Moscow to as far away as Ukraine.
A spokeswoman for Russia's biggest airport, Domodedovo, said 15 planes had been diverted from there after visibility fell dramatically.
Pollution on August 6 surged to five times normal levels in Moscow -- the highest sustained level since Russia's worst heat wave in more than a century began a month ago.
Germany's Foreign Ministry announced it was temporarily closing its embassy in Moscow and warned German citizens against all but essential travel to affected regions in Russia.
Russian military officials said the country's nuclear weapons were safe from the fires, though some nuclear material was evacuated from a facility in Sarov earlier this week.
Russia is experiencing its worse heat wave in more than 100 years and the drought that has accompanied the high temperatures has so damaged Russia's grain crop that the government has suspended exports, substantially driving up world prices for wheat and other grains.
The government has called up army units to help battle the blazes.
compiled from news agencies