Islamic State claimed the assault that killed 150 people and injured more than 600 in Russia’s deadliest attack in over two decades.

Russia on Thursday sentenced 15 men, including four gunmen, to life in prison over the March 22, 2024 attack on the Crocus concert hall near Moscow that left 150 people dead.

The four attackers, Shamsidin Fariduni, Dalerdzhon Mirzoyev, Makhammadsobir Fayzov and Saidakrami Rachabolizoda, all citizens of Tajikistan, carried out the shooting inside the venue before setting the building on fire.

Eleven other men, some of them Russian citizens, were also handed life sentences for acting as accomplices and maintaining terrorist links.

Four additional men, including a father and his sons, received prison terms ranging from 19 to 22 years for their connections to the attackers.

The assault occurred shortly before a concert by Soviet era rock band Picnic. The gunmen opened fire on the crowd and then set the building ablaze, trapping many victims inside. More than 600 people were injured and six children were among those killed.

It was Russia’s deadliest attack since the 2004 Beslan school siege.

The attack took place two years into Russia’s war in Ukraine. Moscow initially dismissed warnings from the United States about a possible imminent attack and later suggested a Ukrainian link, though no evidence was presented.

CBI News reports that Russia’s Investigative Committee said after the verdict that the attack had been planned in the interests of Kyiv and accused the men of also plotting attacks in the Russian region of Dagestan.

The four gunmen, aged between 20 and 31 at the time of the attack, had worked in jobs including taxi driving, factory work and construction.

Hours after the assault, the suspects appeared in court with visible signs of torture, including one who was barely conscious in a wheelchair. Russian media also reported that two suspects had asked the court to allow them to fight in Ukraine instead of serving life sentences.