Gunmen opened fire at a Moscow concert hall on Friday killing at least 40 people, wounding 100 and sparking an inferno, authorities said, with the Islamic State group claiming responsibility.
Attackers dressed in camouflage uniforms entered the building, opened fire and threw a grenade or incendiary bomb, according to a journalist for the RIA Novosti news agency at the scene.
Fire quickly spread through the Crocus City concert hall in Moscow's northern Krasnogorsk suburb, as smoke filled the building and screaming visitors rushed to emergency exists.
Alexei, a music producer, was about to settle into his seat before the start of a rock concert when he heard "several machine gun bursts" and "a lot of screams."
"I realized right away that it was automatic gunfire and understood that most likely it's the worst: a terrorist attack," said Alexei, who would not give his last name.
As people ran towards emergency exists in the concert hall, "there was a terrible crush" with concert goers climbing on one another's heads to get out, he added.
Russia's FSB security service said at least 40 people were killed and more than 100 others injured, according to Russian media reports.
Authorities said a "terrorist" investigation had been started and President Vladimir Putin was receiving "constant" updates, his spokesman Dmitry Peskov told Russian news agencies.
Russia's national guard said it was on the scene and looking for the perpetrators. An AFP reporter saw police officers with sniffer dogs inspecting vehicles parked next to the building.
The Islamic State group said its fighters attacked "a large gathering" on Moscow's outskirts and "retreated to their bases safely."
Telegram news channels Baza and Mash, which are close to security forces, showed video images of flames and black smoke pouring from the hall.
Other images showed two men walking through the hall with at least one person left on the ground near the entrance. Concert-goers were also seen hiding behind seats or trying to escape.
Security services quoted by Interfax said between two and five people "wearing tactical uniforms and carrying automatic weapons" opened fire on guards at the entrance and then started shooting at the audience.
"People who were in the hall were led on the ground to protect themselves from the shooting for 15 or 20 minutes," the RIA Novosti journalist was quoted as saying.
