The U.S. embassy in Moscow issued a security alert warning Americans in Russia to avoid large crowds, including concerts, for the next 48 hours after they learned that extremists were planning an attack.
Six other nations issued a similar warning. The alert came hours after the Russian Federal Security Service (FSB) said they had foiled an attack on a Jewish synagogue by Islamic State terrorists.
It's unclear whether the two threats are connected.
"Active search measures established that they were militants of an international terrorist organization preparing an attack on the congregation of a synagogue with the use of firearms," the FSB statement reads.
"During an operation to detain them, the terrorists put up armed resistance to Russian FSB staff and as a result were neutralized by return fire," it continues.
A State Department spokesperson told Newsweek that there was "no higher priority than the safety and security of U.S. citizens overseas" but refused to say whether the foiled synagogue attack and the security alert were connected.
The FSB said an Islamic State cell was operating in Russia's Kaluga region as part of the Afghan arm of the group, which is known as ISIS-Khorasan and seeks a caliphate across Afghanistan, Pakistan, Turkmenistan, Tajikistan, Uzbekistan and
The group first appeared in eastern Afghanistan in late 2014 and established a reputation for extreme brutality.
The cell "was preparing to attack the congregants of a synagogue using firearms," the FSB said.
When tackled, the militants offered resistance by Russian special forces and were "neutralised" by return fire, it said.
Russia, ever paranoid, accused the U.S. and Great Britain of planning a "false flag" terror attack and then blaming it on ISIS.
This week's warning prompted several Putin allies in Russia to launch evidence-free conspiracy theories claiming that the U.S. and U.K. were planning to commit terror attacks in Russia and blame the attacks on another entity.
"The USA and Britain have even stopped hiding that they are behind the terrorist attacks in Russia," a post on the pro-Kremlin Telegram channel RIA Katyusha reads.
Margarita Simonyan, the editor-in-chief of Russian state-run media outlet RT, reportedly suggested that the U.S. and U.K. would be guilty of "complicity" in future terror attacks occurs in Russia if "specific information" is not "passed on" to the Kremlin.
What's unusual about those warnings, and not a little unsettling, is their specificity and the 48-hour time frame. It's not common for an embassy to share that kind of specific intelligence with citizens unless the threat is real and imminent.
The threat may not be coming from ISIS-K. If that's the case, Russia has a bigger problem. At least two deadly terror groups have active, operational cells within the Russian Federation.
Publicizing the threat may not be enough to stop it.
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