The U.S. Embassy in Moscow issued a security alert Saturday warning people of a potential "mass casualty event" at the 2 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 2 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, get 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 cellphone batteries and other batteries charged, remain aware of surroundings and 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.

The Trump administration warned Iran that there "will be consequences" if Tehran continues its malign activities amid growing concern over a potential new round of U.S.-Iran hostilities after the midterm elections.

With just days until the 2026 elections and with war raging on in the Middle East, foreign ministers from the world's largest economies gathered in Atlanta, Georgia ahead of the G20 leaders meeting in December.

"The Iranian regime has had a choice... to either pursue the path towards normalcy, towards prosperity for their people, the path towards diplomacy. Or they can continue their malign activities, but there will be consequences for that, and we've seen the president taking concrete action," State Department principal deputy spokesperson Tommy Pigott told Fox News Digital on Friday.

Pigott was responding to reports that U.S. officials have warned regional partners to prepare for the possibility of heightened U.S. military action against Iran after Tuesday's elections, as well as potential Iranian retaliation.

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President Donald Trump has not made a final decision on renewed strikes, but U.S. diplomats and defense officials have privately urged several Middle Eastern countries and regional allies to prepare for the possibility of new military action and Iranian retaliation, according to an Associated Press report citing two diplomats briefed on the warnings.

The warnings come amid heightened concerns about Iranian threats against Americans overseas.

Director of National Intelligence Jay Clayton wrote in an unclassified memo to Secretary of State Marco Rubio that the U.S. had received intelligence that Iran had "substantially increased efforts to target U.S. personnel" and that lethal Iranian plots had reached "advanced stages" in the Middle East and elsewhere, according to Scripps News.

Asked whether those threats were being discussed with G20 counterparts and whether the U.S. was sharing intelligence with allies to disrupt potential plots, Pigott declined to discuss intelligence matters but said the U.S. was working with international partners against transnational threats.

"We're going to work with our partners to make sure that any transnational threat has the appropriate transnational response to protect our citizens," he insisted.

The prospect of renewed fighting with Iran loomed over the G20 foreign ministers' meeting, where Rubio has put energy security, secure supply chains and freedom of navigation among the U.S. priorities.

Rubio opened the two-day gathering Friday by warning that the world's largest economies face "interconnected economic and geopolitical crises" threatening energy and food supplies, trade, global supply chains and freedom of navigation.

Pigott said the administration's position remains that "there cannot be a situation where a country decides that they can control an international waterway and charge tolls over that waterway."

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In the aftermath of the war, Iran began asserting greater authority over the Strait of Hormuz and insisting on the right to collect fees from ships for services including navigation and environmental protection.

Asked what the U.S. wants G20 countries to do to keep the strait open, Pigott pointed to a broader principle that international waterways must remain free from coercion.

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"Fundamentally, the principle here is so important, making sure that we are having secure international waterways in the sense we're not having these tolls or coercion, making sure we have secure supply chains," Pigott said. "That is so important."