Russia's top domestic security agency says it has tracked down a group of suspects accused of forging personal documents for Islamic State group militants.

The Federal Security Service, or FSB, said in Thursday's statement that it has arrested 14 suspected members of the group during a raid in the Moscow region.

The FSB said the suspects were forging documents for Russians willing to join IS in Syria and also making papers for IS militants sent to Russia to carry out terror attacks.

Russian President Vladimir Putin has described the IS threat to Russia as a key factor behind his decision to launch airstrikes on militants in Syria. He said between 5,000 and 7,000 people from Russia and other former Soviet countries are now fighting alongside Islamic State militants.