The U.S. Embassy in Moscow issued a security alert Saturday warning people of a potential "mass casualty event" at the Tsaritsyno Museum Reserve in Moscow.

"The U.S. Embassy in Moscow is aware of a credible threat of a mass casualty event TODAY October 31, at the Tsaritsyno Museum Reserve in Moscow at Dolskaya Ulitsa 1, Moscow, Russia 11569. The U.S. government is coordinating with appropriate Russian authorities on a response," the embassy wrote in a statement.

The alert warned people to avoid the Tsaritsyno Museum area and to "stay alert, and avoid crowds."

Founded in 1775 as a summer home for Russia's Catherine II, the Tsaritsyno Museum is now a popular tourist attraction in Russia's capital.

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The museum itself attracted more than two million visitors in 2022, Moscow's deputy mayor Natalya Sergunina said in 2023. The surrounding grounds, enjoyed by Moscow's local citizens for physical activity and dog walking, see even more foot traffic, according to The Art Newspaper.

The U.S. Embassy's alert also included a warning to people in the Moscow area to keep cell phones and other batteries charged, stay aware of surroundings, and to review a personal security plan.

The alert was issued as tensions in the ongoing war between Russia and Ukraine continue to escalate.

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On Friday, Ukraine struck an oil refinery in southern Russia, ending a two-week pause on energy infrastructure attacks brokered by President Donald Trump between the warring nations.

The previous day, Russian drone and missile strikes in Ukraine killed at least 27 civilians, according to the Wall Street Journal.

Fox News Digital contacted the U.S. Embassy in Moscow for further information.

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This is a developing story. Please check back for updates.