U.S. warns of imminent Moscow attack by ‘extremists,’ urges citizens to avoid crowds

U.S. citizens in Moscow have been warned to avoid large gatherings Friday and Saturday because of heightened fears of a terrorist attack.

The U.S. Embassy in the Russian capital said it was “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.”

U.S. citizens should avoid crowds, monitor local media for updates and “be aware of your surroundings,” it said in a brief online update.

The embassy did not elaborate on who or what poses the apparent threat to the Russian capital, or what kind of attack may be imminent.

But Russia’s FSB security service said Thursday that it had foiled a planned attack by an Afghan offshoot of the Islamic State terrorist group on a synagogue in the Kaluga region, southwest of Moscow.

“On the territory of the Kaluga Region, a stop was put to the activity of Wilayat Khorasan, a cell of the Afghan branch of the international terrorist organization Islamic State, which is banned in Russia, whose members were planning to commit a terrorist act against one of the Jewish religious institutions in Moscow,” the FSB said in a statement given to the state-run Tass news agency.

The FSB said the group was planning to shoot members of the congregation. It added that its officers engaged in a firefight with the militants before its officers “neutralized” them.

The case is being investigated in Russia as a conspiracy to conduct a terrorist attack. The FSB said it searched a building used by the group and found firearms, ammunition and materials for making an improvised explosive device.

It was not immediately clear if the FSB statement was linked to the U.S. Embassy warning.

The U.S. has repeatedly urged its citizens to leave Russia, as relations between the two countries spiral over the Kremlin’s invasion of Ukraine and the imprisonment of a number of Americans in Russian jails.

​Separately, on Thursday, the U.S. Embassy in Moscow strongly criticized Russia for designating three American educational and exchange organizations as “undesirable,” ending a tradition of young people traveling to each other’s country that dates back 70 years.

The embassy said the decision was “a tragic illustration of the Kremlin’s desire to isolate its own people, depriving them of the chance to network, expand their horizons, and contribute to building a more prosperous and peaceful world.”

Russia said it had summoned American Ambassador Lynne Tracy to tell her that the three nongovernmental organizations would be banned for “implementing anti-Russian programs and projects aimed at recruiting ‘agents of influence’ under the guise of educational and cultural exchanges.”

This article was originally published on NBCNews.com