Russia's counterterrorism agency yesterday raided a Moscow apartment and arrested several Russians who allegedly were preparing to carry out an attack in the capital.
The FSB intelligence agency said in a statement on Monday that an improvised explosive device with five kilos (11 pounds) of unidentified explosives was found in that apartment.
The FSB said several men were detained, including two who said they had been trained by Islamic State militants and were plotting a terrorist attack on Moscow's public transport.
More than 100 residents of the apartment building in western Moscow were evacuated during yesterday's raid and supplies of natural gas were cut off for the duration.
Russia's airstrikes in Syria have been met by warnings that they encourage Islamic extremists to turn their sights on Russia and make it easier for them to recruit Russian Muslims. Russia says 2,400 of its citizens have joined the Islamic State group.