PEREDELTSY, Russia — Moscow was engulfed Wednesday by the thickest blanket of smog yet this summer, an acrid, choking haze from wildfires that have wiped out Russian forests, villages and a military base.
Passengers on Moscow's subway said the eye-stinging haze hovered above the platforms, and City Hall warned of health risks from the smoke, which is carrying harmful gases, including carbon monoxide.
"I woke up before dawn and thought I was going to die of suffocation," said Yadviga Pashkova, a frail, 62-year-old former schoolteacher who lives in central Moscow. "It felt awful because there was no way out."
To the east, firefighters focused on beating flames back from a top-secret nuclear research facility. In the capital, President Dmitry Medvedev fired several high-ranking military officials over what he called criminal negligence in fires that ravaged a military base.
Russia is suffering through its worst heat wave on record, a condition that has sparked forest and peat fires across its central and western regions that have killed at least 48 people in the past week. Temperatures for weeks have soared as high as 100 in Moscow, where the average summer temperature usually is around 75.
Over the past 24 hours, firefighters have extinguished 293 fires, but 403 others have been spotted and more than 500 others have continued to rage over large swathes of countryside, some of them out of control, the Emergencies Ministry said.
Dry winds have sent clouds of smog over Moscow before, but Wednesday's was the worst yet, with the haze obscuring the capital's landmarks and penetrating the subway system.
Moscow's 10 million residents were cautioned to protect themselves against the polluting smog, which came from wildfires in forests and peat bogs to the south and east. The bogs were drained in Soviet times to harvest peat, leaving them prone to fires.
Pollution indicators in the capital reached a "critical barrier" overnight, and "even healthy people must take preventative measures," Moscow weather officials said. Residents were urged to wear face masks outdoors.