UN human rights chief Volker Turk was "horrified" by the deadly Moscow concert hall attack, his office said Saturday as it called for the perpetrators to be held to account.

Russia said it had arrested 11 people -- including four gunmen -- over Friday's attack on the Crocus City Hall which left at least 115 dead. The attack has been claimed by the Islamic State jihadist group.

"Nothing justifies such an attack. Perpetrators must be held accountable in line with human rights law. Our solidarity with the victims of this shocking violence," the UN Human Rights Office said on X, formerly Twitter.

Camouflaged gunmen opened fire at the packed hall in Moscow's northern suburb of Krasnogorsk ahead of a concert by rock band Piknik in the deadliest attack in Russia for at least a decade.

UN Secretary General Antonio Guterres and the UN Security Council earlier made the "strongest" condemnations of the attack and offered condolences to the victims of the "terrorist" incident.