A senior Russian diplomat says far more than 800 Russians are fighting alongside the Islamic State group.

Ilya Rogachev, who heads the Foreign Ministry's department for modern challenges and threats, told Ekho Moskvy radio Friday that those who have joined the group include people from the Russian province of Chechnya and some other regions in the volatile North Caucasus.

He said precise numbers of Russians among the Islamic State fighters are hard to measure, as they include some Chechen refugees who had moved to Europe, as well as some ethnic Chechens from Russia's ex-Soviet neighbor, Georgia.

Chechnya, which has seen two devastating separatist wars, has become more stable under the steely grip of a Moscow-backed strongman, but the Islamist insurgency has engulfed other North Caucasus provinces.