Green clouds hovering over Moscow had people in a panic on Thursday, as officials rushed to explain that the looming clouds were the result of birch pollen, not chemicals from an allegedly burning factory in the region, RT News reported.
"Today Muscovites felt like characters in a disaster film about an alien invasion: people living in the southwest of the city saw that the sky had been colored green," said Russia's weather service on its website, Agence France Presse reported.
The city's tabloid newspaper, Komsomolskaya Pravda, fuelled the unease with its headline "Green clouds are coming toward Moscow, could it be that the apocalypse is upon us?" the Daily Mail reported.
The greenish clouds swept over the city as the region observed the 26th anniversary of Chernobyl, the world's worst nuclear disaster, the Associated Press reported.
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The Soviet government initially tried to hide the chemical explosion at Chernobyl, and failed to explain the events to the public or tell residents and cleanup workers how to protect themselves against radiation, according to the AP.
Though many feared apocalyptic scenarios, the eerie green pollen clouds appeared when a cold period that extended into April shifted into much warmer temperatures last week, Moscow's Emergency Situations Ministry said, according to Ria Novosti News.
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The warm weather and a wind from the south caused several species of trees to bloom, resulting in a yellow-green pollen coating over pavement, windows, and cars, AFP reported.
"Many residents forgot all about natural phenomena and decided that it's the result of an accident at an industrial facility," a spokesperson from the city administration of Podolsk, an industrial town south of Moscow, told the AFP.