'Nuclear Mushroom' Cloud in Southern Russia Freaks Out Locals

Frightened residents of Kazan, Russia's fifth-largest city, have taken to social media to share pictures and videos of a cloud that resembles a "nuclear mushroom", local media reported.

Residents of Kazan, the capital of the Republic of Tatarstan, said they saw an "eerie" mushroom-shaped cloud in the skies on Wednesday evening that resembles the shape observed after a nuclear explosion. Local news outlet Vechernyaya Kazan later said that the meteorological phenomenon is a "cumulonimbus" or "anvil" cloud.

A cumulonimbus is a dense, vertical cloud containing a thunderstorm, formed from warm, moist, and unstable air that rises and overturns upwards. This causes the cloud top to flatten and spread into an anvil or a mushroom shape. NASA says this type of cloud is more likely to form in tropical latitudes year-round and during the summer season at higher latitudes.

State-run news agency RIA Novosti interviewed a spokesperson for the Republic of Tatarstan's Ministry of Ecology and Natural Resources who sought to ease residents' fears after the mushroom-shaped formation was spotted in the skies. The cloud, resembling a "nuclear mushroom" is a kind of cumulonimbus, the spokesperson said.

"Warm air is lighter than cold air. Its rise into the middle layers of the atmosphere can be seen in the form of a mushroom cloud. This atmospheric phenomenon is called an inversion, or an anvil cloud. This is a special type of cumulonimbus cloud that rises to a height of about 12 to 15 kilometers [7.4 to 9.3 miles], and then begins to blur," the spokesperson said.

Tensions are at a high in Russia, more than 17 months into Russian President Vladimir Putin's full-scale invasion of Ukraine.

Putin has threatened the use of nuclear weapons, saying in September in a televised address to the nation that he'd be prepared to use them to defend Russian territory.

"If the territorial integrity of our country is threatened, we will without doubt use all available means to protect Russia and our people—this is not a bluff," Putin said at the time.

There have been growing fears throughout that conflict that Russia may issue fresh nuclear threats if Ukraine attempts to recapture Crimea, the Black Sea peninsula that Putin illegally annexed in 2014.

Many fear the retaking of Crimea by the Ukrainians would be a red line for Russia and that Putin may use his country's nuclear capabilities to defend the territory.

Ukrainian President Volodymyr Zelensky has vowed to take back the peninsula, which has been subject to growing strikes in recent weeks. These include a second attack last month on the strategically vital Kerch Bridge, which links Russia to Crimea. Kyiv has claimed responsibility for both strikes.

Newsweek has contacted Russia's Foreign Ministry via email for comment.

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