Overview

• Russia observes a national day of mourning following the deadly attack on a Moscow concert hall, with the death toll surpassing 130.
• Islamic State claims responsibility for the massacre, marking the deadliest terrorist act in Russia in nearly two decades.
• President Vladimir Putin vows to punish those behind the attack, arresting four suspects allegedly attempting to flee to Ukraine.
• The U.S. confirms Islamic State's sole responsibility for the attack, dismissing any Ukrainian involvement.
• Russian authorities and citizens respond with heightened security measures and tributes to the victims amidst calls for unity against terrorism.