The shooting at Crocus City Hall occurred before a sold-out concert by a Russian progressive rock band, officials said.

Emergency vehicles are parked near the burning Crocus City Hall following a reported shooting incident on Friday. 

The Islamic State group claimed responsibility for Friday's mass shooting at a popular concert hall on the outskirts of Moscow that left dozens dead an injured more than 100 others, the Associated Press reported.

ISIS, which the United States has designated as a terrorist group, said in a message posted Friday night to the Telegram messaging app that it had “attacked a large gathering… on the outskirts of the Russian capital Moscow," and that the attackers had "retreated to their bases safely," according to the Moscow Times. Those claims could not be independently verified, however.

What happened

Fiday's shooting occurred at Crocus City Hall in Krasnogorsk, west of central Moscow. RIA Novosti, a Russian state-run news agency, reported that “at least three people in camouflage burst into the ground floor” of the venue and “opened fire with automatic weapons,” wounding multiple people.

The Associated Press, citing the Federal Security Service, reported that at least 40 people were killed and over 100 others injured in the attack.

Videos posted to social media and confirmed by U.S. news outlets showed men with rifles moving through the concert hall. Photos and videos from the scene showed the concert hall engulfed in flames.

According to NBC News, the Russian progressive rock band Picnic was scheduled to perform a sold-out show at the 9,500-seat venue on Friday. According to officials, the shooting occurred before the start of the show.

Who is Islamic State?

Friday evening, the Islamic State group came forward on Telegram to claim responsibility for the attack.

Primarily based in Iraq and Syria, the Islamic State and its offshoots are a Sunni jihadist group. They also operate also in Afghanistan and Africa and have been known to recruit fighters from Russia.

What are other Russian authorities saying?

A spokesperson for Igor Krasnov, Russia's prosecutor general, said in a Telegram post that he was headed to the scene and that officials were working to determine the number of fatalities.

"Tonight, before the start of the event in the concert hall in Krasnogorsk, unknown men in camouflage clothes broke into the building and started shooting," the post added. "The number of victims is being determined, a fire started in the entertainment center building, and citizens are being evacuated."

Moscow Mayor Sergei Sobyanin said he was canceling all public events in Moscow this weekend.

"I have taken the decision to cancel all sports, cultural and other public events in Moscow this weekend," Sobyanin said in a Telegram post. "I ask of you to treat this measure with understanding."

U.S. had warned of possible ‘extremist’ attacks

Earlier this month, the U.S. Embassy in Moscow issued a security alert warning that it was “monitoring reports that extremists have imminent plans to target large gatherings in Moscow,” including concerts.

The March 7 statement advised U.S. citizens in the Moscow area to “avoid large gatherings over the next 48 hours.”

According to Reuters, the embassy issued its warning several hours after Russia's Federal Security Service (FSB) said it “foiled an attack on a synagogue in Moscow by a cell of the militant Sunni Muslim group Islamic State.”

Shooting comes on heels of Putin's reelection

Friday's deadly attack comes less than a week after Russian President Vladimir Putin won a fifth term in a landslide election that U.S. and other Western leaders denounced as a sham.

It also comes amid Russia's ongoing war against Ukraine, now in its third year.

Hours before Islamic State took responsibility for Friday's mass shooting, Mykhailo Podolyak, an advisor to Ukrainian President Volodymyr, denied that his country was in any way involved in the attack.

“Ukraine certainly has nothing to do with the shooting/explosions in the Crocus City Hall (Moscow Region, Russia),” Podolyak wrote on X. “It makes no sense whatsoever.”

U.S. National Security Council spokesperson John Kirby echoed Podolyak's denial.

“There is no indication at this time that Ukraine, or Ukrainians, were involved in the shooting, but again, this just broke," Kirby told reporters Friday afternoon. "We’re taking a look at it, but I would disabuse you at this early hour have any connection to Ukraine.”