KYIV, June 5 (Reuters) - Two armed groups, the Russian Volunteer Corps (RVC) and Freedom of Russia Legion, say they have carried out attacks in Russia's western Belgorod region in recent weeks. Kyiv has denied any role and said the attackers are Russian citizens. Here is what we know about the groups. RUSSIAN VOLUNTEER CORPS The RVC was founded by a far-right Russian national last August and comprises Russians who have been fighting in and for Ukraine against their own country. It said on Sunday it was also behind an attack in the Belgorod region in which several soldiers were...