Assailants burst into a large concert hall in Moscow on Friday and sprayed the crowd with gunfire, killing over 60 people, injuring more than 100 and setting fire to the venue in a brazen attack just days after President Vladimir Putin cemented his grip on power in a highly orchestrated electoral landslide.

The Islamic State group claimed responsibility for the attack in a statement posted on affiliated channels on social media. A U.S. intelligence official told The Associated Press that U.S. intelligence agencies had learned the group’s branch in Afghanistan was planning an attack in Moscow and shared the information with Russian officials.

It wasn’t immediately clear what happened to the attackers after the raid, which state investigators were investigating as terrorism.

The attack, which left the concert hall in flames with a collapsing roof, was the deadliest in Russia in years and came as the country’s war in Ukraine dragged into a third year. Moscow Mayor Sergei Sobyanin called the raid a “huge tragedy.”