Hunt says UK should 'absolutely' be concerned about Islamic State after Moscow attack

US Intelligence Confirms , IS Involvement With Deadly , Moscow Concert Attack. On March 22, an attack on Russia's Crocus City Hall concert venue killed at least 137 people. . Associated Press reports that an affiliate of the Islamic State has claimed responsibility for the attack, which was the deadliest to occur on Russian soil in years. Four suspects were arrested on March 23, with seven other detained on suspicion of having some involvement with the attack. . Four suspects were arrested on March 23, with seven other detained on suspicion of having some involvement with the attack. . In an address to the nation, Russian President Vladimir Putin looked to tie the attack to Ukraine, claiming that assailants were captured while fleeing to Kyiv. . In an address to the nation, Russian President Vladimir Putin looked to tie the attack to Ukraine, claiming that assailants were captured while fleeing to Kyiv. . On March 24, events at cultural institutions across Russia were canceled and flags were lowered to half-staff. . On March 24, events at cultural institutions across Russia were canceled and flags were lowered to half-staff. . State news agencyy RIA Novosti announced that television and advertising had also been suspended. Rescue workers continue to search for the site of the attack, while the death toll rises as more bodies are found in the damaged building. . Moscow's Department of Health said on March 24 that the process of identifying the bodies of victims by DNA testing would take at least two weeks. AP reports that United States intelligence officials confirmed the Islamic State (IS) affiliate's responsibility for the attack, while refuting Putin's claim that it was tied to Ukraine. AP reports that United States intelligence officials confirmed the Islamic State (IS) affiliate's responsibility for the attack, while refuting Putin's claim that it was tied to Ukraine. ISIS bears sole responsibility for this attack. There was no Ukrainian involvement whatsoever, Adrienne Watson, National Security Council spokeswoman, via Associated Press. ISIS bears sole responsibility for this attack. There was no Ukrainian involvement whatsoever, Adrienne Watson, National Security Council spokeswoman, via Associated Press