(CNN) -- About 270 new wildfires have started in drought-plagued Russia over the past 24 hours, state media reported Sunday, citing the country's emergencies ministry.
"As many as 276 wildfires have been extinguished," the ministry told RIA-Novosti. "Currently, 554 wildfires are raging on an area of over 190,000 hectares."
The setback comes as Moscow chokes in intense smog, with toxic substances at levels several times greater than the norm. State media reports the combination of forest fires and pollutants contributed to the smog.
According to Russia's health and social development ministry, wildfires have killed at least 52 people and left dozens hospitalized.
Russian President Dmitry Medvedev donated almost $12,000 of his personal funds to support people affected by wildfires raging across Central Russia, his website said Saturday.
Hundreds of passengers have been stranded due to delayed flights at the Domodedovo international airport in Moscow. Poor visibility caused by the wildfire smog has prevented airplanes from taking off, said airport officials quoted by the Itar-Tass news agency.
High temperatures in the past several weeks have caused a destructive drought as well as fires that changed the forecast for Russia's grain production.
The situation led the government to impose a temporary ban on exports of grain and grain products, said RIA-Novosti. The trade ban will go into effect August 15.
Moscow saw the worst air pollution of the year Saturday, state media reported. Carbon monoxide levels were more than six times the maximum allowable concentration, and other toxic substances permeated the city air at nine times the normal level.
CNN's Mila Sanina contributed to this report.