The U.S. Embassy in Moscow is warning American citizens in Russia's capital city to avoid large gatherings Friday and Saturday over concerns about a potential terror attack. 

In an alert posted Thursday, the embassy said it “is monitoring reports that extremists have imminent plans to target large gatherings in Moscow, to include concerts, and U.S. citizens should be advised to avoid large gatherings over the next 48 hours.”

The warning also advises U.S. citizens to monitor local media reports for updates and to be aware of your surroundings.

The advisory did not include any other details about the threat. 

The U.S. has repeatedly urged its citizens to leave Russia amid growing tensions between the two countries over Russia’s invasion of Ukraine two years ago and the United States’ support of Kyiv in the war.

The embassy’s warning came on the same day that Russia’s Federal Security Service said it foiled a plot by an Islamic State-linked group to attack a synagogue in Moscow. 

“A stop was put to the activity” by the group, Wilayat Khorasan, in Russia’s Kaluga region, just southwest of Moscow, the Federal Security Service said in a statement, Russian news agency TASS reported.

The statement also said the terror group “put up armed resistance to Russian FSB staff and as a result were neutralized by return fire."

It’s not clear if that incident and the U.S. warning are related.