MOSCOW — Russia's Federal Security Service (FSB) said it had received information from the United States through established partner channels about preparations for a terrorist attack in Moscow and was taking appropriate measures, Reuters reported on Saturday.

Source: Reuters, Oct 31, 2026

The US Embassy in Moscow said separately that it was 'aware of a credible threat of a mass casualty event' on Saturday at Moscow's Tsaritsyno Museum Reserve and that the US government was coordinating with Russian authorities, according to Reuters. The embassy's security alert named the site at Dolskaya Ulitsa 1, told Americans to avoid the area that day and to avoid crowded places, and did not say who might be behind the threat or how an attack might be carried out.

Source: US Embassy Moscow security alert, via Clash Report, Oct 31, 2026

The Tsaritsyno Museum Reserve, a palace museum and park complex in southern Moscow, has been temporarily closed and access to the park is currently restricted, the RIA news agency reported, citing Russian law enforcement agencies. The FSB did not say whether its information concerned Tsaritsyno specifically, and no detentions or other operations linked to the threat had been reported at the time of the reports.

Oct 31day named in the US Embassy alert for the Tsaritsyno Museum Reserve in Moscow
1 site namedTsaritsyno Museum Reserve, Dolskaya Ulitsa 1 — temporarily closed, park access restricted, RIA reported
0 reportedattacks, detentions or casualties linked to the threat in the reports available

The public warning-and-confirmation sequence between Washington and Moscow is rare, and it carries a recent precedent. In March 2024, the US Embassy warned that extremists had imminent plans for an attack in Moscow; days later, gunmen attacked the Crocus City Hall concert venue outside Moscow, killing more than 140 people, Reuters noted.

Neither the embassy nor the FSB has described the nature of the threat, and the FSB has not said what measures it is taking. Readers should treat this as a threat warning, not an attack: as of the latest reports on Saturday, no incident had taken place at the site.