Russia detains suspects in an attack that left at least 115 dead in a Moscow concert hall

Russian President Vladimir Putin said Saturday that authorities have detained 11 people in the attack on a suburban Moscow concert hall that killed at least 115 people and left the sprawling venue a smoldering ruin.

In an address to the nation, Putin called it "a bloody, barbaric terrorist act" and said all four people who were directly involved had been taken into custody. He suggested they had been trying to cross the border into Ukraine, which, he said, tried to create a "window" to help them escape.

Ukraine has vehemently denied any involvement in the attack. Putin said Saturday that additional security measures have been imposed throughout the country and declared March 24 a day of national mourning.

The Islamic State group's Afghanistan branch claimed responsibility for Friday's attack in a statement posted on affiliated channels on social media. A U.S. intelligence official told The Associated Press that U.S. agencies had confirmed that the group was responsible for the attack.

The attack, which was the deadliest in Russia in years, came just days after Putin cemented his grip on power in a highly orchestrated electoral landslide and as the country's war in Ukraine dragged into a third year.

Some Russian lawmakers pointed the finger at Ukraine immediately after the attack. But 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."

Ukraine's foreign ministry also denied that the country had any involvement and accused Moscow of using the attack to try to stoke fervor for its war efforts.

"We consider such accusations to