The attack on the Crocus City Hall on Friday killed at least 133 people and injured more than 100. Russian authorities expected the number of casualties to rise.

The blaze ripped through the venue, with smoke filling the building and screaming visitors rushing to emergency exits.

The concert hall, one of the most popular in Moscow, can hold some 6,200 people.

Graphic videos posted on social media showed the gunmen firing repeated rounds as they entered the building, shooting at screaming people at point-blank range.

Helicopters were brought in to douse the flames from the air, as firefighters battled the flames from the ground. The fire was eventually brought under control early on Saturday.

The Emergency Situations Ministry said firefighters helped about 100 people escape through the building’s basement, while rescue operations were also launched for people trapped on the roof.

ISIS-K, an offshoot of ISIL (ISIS), the hardline group that once sought control over Iraq and Syria, claimed responsibility for the attack on its Telegram channel, saying the gunmen had escaped.

Russian investigators said on Saturday that 11 people had been detained so far.