The U.S. Embassy in Russia issued a warning on March 7 that "extremists have imminent plans to target large gatherings in Moscow" and urged American citizens to stay away from concentrations of people over the next 48 hours. The embassy did not specify what kind of threats they referred to, or who might be behind them. The U.K. Embassy in Russia also repeated the advisory issued by the U.S. Russia's Federal Security Service (FSB) said on March 7 that its agents had thwarted a potential Islamic State terrorist attack on a Moscow synagogue. The Russian state-owned TASS news agency said that FSB agents had killed several militants who were planning the attack, citing the FSB's press office. It is unclear if the incident is related to the U.S.'s warning.