MOSCOW (AP) — Russia's main intelligence agency says it has detained four men from a Siberian oil town who are linked to the Islamic State group and are suspected of plotting terror attacks in Moscow.

The FSB agency said Friday that the four members of the suspected IS "sleeper cell" were detained in the Moscow region after they traveled from Novy Urengoi, an oil town in western Siberia. The FSB said the men plotted attacks in Moscow and were receiving orders from IS members in Syria via a messaging app.

Twenty people were detained in Novy Urengoi on suspicion of aiding the group.

Russia has been providing air cover for Syrian President Bashar Assad since 2015, while thousands of its own citizens went off to Syria to join IS in fighting against Assad's government.