The Daesh terrorist group claimed responsibility for the attack on a concert hall in Russia's capital Moscow, which killed at least 133 people late Friday.
"The attack was carried out by four Daesh fighters armed with machine guns, a pistol, knives and firebombs," Daesh said on one of its Telegram channels.
The terrorists had already said on Friday night they carried out the attack and claimed their fighters had "returned to base safely."
The Kremlin, which has not reacted to the terrorist group's claim, said 11 people had been arrested "including four terrorists" involved in the attack.
Russian officials have suggested the attackers had links to Ukraine, a claim labeled as "absurd" by Kyiv.
Russia is fighting Daesh in Syria and the terrorist group has also had a presence in the Muslim-majority Russian republics of Ingushetia, Dagestan and Chechnya.
The group has carried out attacks in Russia but has never before said it was behind such a major atrocity.
