Russian authorities claimed to have foiled a major terrorist plot on Monday, allegedly planned by men trained at Islamic State camps in Syria and aimed at Moscow’s busy public transport system.

Information about the alleged terrorists remained murky on Monday evening. An official statement from the FSB said only that a raid had taken place on an apartment where between six and 11 people lived, “some of whom have been through combat training in Islamic State camps in Syria.” The FSB said they were all Russian citizens.

It was unclear if any of the group were still at large. Those arrested could face up to 20 years in prison.

Television footage of the police raid showed police carrying sacks out of the building, including a washing machine. The FSB said it seized 5kg of explosives that had been prepared and were ready to use, complete with a phone-activated detonator.

“During questioning of two of the detained men, it became known that they were planning a terrorist attack on the Moscow public transit system,” the FSB said.

Previously, terrorists from the North Caucasus have targetted the metro system, a train station and an airport in the capital, but Moscow has not seen a major attack for nearly five years, since a suicide bomber killed 37 people at Domodedovo Airport in 2011.



The agency said the men had arrived in Russia long before Moscow’s bombing campaign in Syria, which some have speculated could increase the terrorism threat inside Russia.



There has been speculation that Russia’s decision to enter the conflict in Syria could make it a target for terrorist acts, although some analysts have pointed out that the simmering insurgency in the North Caucasus is much weaker now, partly because many of the Islamic radicals have left the country to fight in Syria.



Russian officials have said there are around 2000 Russians fighting in the ranks of the Islamic State in Syria, many of them from Muslim regions such as Chechnya and Dagestan. Moscow has said it is fighting Islamic State in Syria, but reports from the ground suggest Russian planes are targeting other rebel groups opposed to the government of Bashar al-Assad.

Some Russians expressed cynicism over initial reports that police found the apartment because a watchful resident had overheard men talking about a “detonator” in the stairwell. LifeNews, an agency with links to the security services, later reported that the men the vigilant resident had spotted were in fact FSB agents who were already at the scene.