MOSCOW (AP) Russian authorities detained 11 people, state media reported Saturday, after gunmen stormed a concert hall in Moscow in a grisly attack that left at least 115 people dead.

Russias Investigative Committee said four of those detained were directly involved in the attack that left the sprawling shopping mall and music venue smoldering with a collapsed roof.

Russian agencies appeared to suggest the attack was linked to Ukraine even though the Islamic State group claimed responsibility in a statement. A U.S. intelligence official told The Associated Press that U.S. agencies had confirmed that that group was responsible for the attack.

The four suspects were stopped in the Bryansk region of western Russia, not far from the border with Ukraine, Russias Investigative Committee said. They planned to cross the border into Ukraine and had contacts there, state news agency Tass said, citing Russias FSB. The head of the FSB briefed President Vladimir Putin on the arrests on Saturday, according to Tass.

The attack came just days after Putin cemented his grip on power in a highly orchestrated electoral landslide. The attack was the deadliest in Russia in years and came as the countrys fight in Ukraine dragged into a third year.

Shortly after the attack, some Russian lawmakers pointed the finger at Ukraine. Mykhailo Podolyak, an adviser to Ukrainian President Volodymyr Zelenskyy, denied any involvement.

Ukraine has never resorted to the use of terrorist methods, he posted on X, formerly Twitter. Everything in this war will be decided only on the battlefield.