MOSCOW (AP) — A trial began Monday under tight security for 19 defendants accused of involvement in last year’s shooting rampage in a Moscow concert hall that killed 149 people and wounded over 600 in one of the deadliest attacks in the capital in years.

A faction of the Islamic State group claimed responsibility for the March 22, 2024, massacre at the Crocus City Hall concert venue in which four gunmen shot people who were waiting for a show by a popular rock band and then set the building on fire.

President Vladimir Putin and other Russian officials have claimed, without presenting evidence, that Ukraine had a role in the attack. Kyiv has strongly denied any involvement.

The Investigative Committee, Russia's top criminal investigation agency, said in June that it concluded that the attack had been “planned and carried out in the interests of the current leadership of Ukraine in order to destabilize political situation in our country.” It also noted the four suspected gunmen tried to flee to Ukraine afterward.

The four, all identified as citizens of Tajikistan, were arrested hours after the attack and later appeared in a Moscow court with signs of being severely beaten.

The defendants appearing in court on Monday kept their heads bowed as they sat in the defendants' cage.

The committee said earlier this year that six other suspects were charged in absentia and placed on Russia’s wanted list for allegedly recruiting and organizing the training of the four. Other defendants in the trial were accused of helping them.