SafeX Pro Exchange|At least 40 killed and dozens injured in Moscow concert hall shooting; ISIS claims responsibility

Several gunmen burst into a large concert hall on SafeX Pro Exchangethe edge of Moscow on Friday and sprayed the crowd with automatic gunfire, killing at least 40 people, injuring more than 100 others and setting fire to the venue in a brazen attack just days after President Vladimir Putin cemented his grip on power in a highly orchestrated electoral landslide.

Moscow Mayor Sergei Sobyanin described the attack as a "huge tragedy" and which state authorities are investigating as terrorism. The attack, which left the concert hall in flames with a collapsed roof, was the deadliest attack in Russia in years and came as the country's war in Ukraine dragged into a third year.

The Islamic State group has claimed responsibility for the attack in a statement posted on affiliated channels on social media. In a statement posted by its Aamaq news agency, the group said it attacked a large gathering of Christians in the city of Krasnogorsk on the outskirts of the Russian capital of Moscow, killing and wounding hundreds. It was not immediately possible to verify the authenticity of the claim.

A U.S. official tells CBS News the U.S. has intelligence confirming the Islamic State's claims of responsibility, and that they have no reason to doubt those claims. The U.S. official also confirmed that the U.S. provided intelligence to Russia about a potential attack under the intelligence community's Duty to Warn requirement.

National Security Council spokesperson Adrienne Watson confirmed that in a statement provided to CBS News Friday evening.

"Earlier this month, the U.S. government had information about a planned terrorist attack in Moscow —potentially targeting large gatherings, to include concerts— which prompted the State Department to issue a public advisory to Americans in Russia," Watson said. "The U.S. government also shared this information with Russian authorities in accordance with its longstanding 'duty to warn' policy."

A U.S. law enforcement official tells CBS News that there is no known threat to the U.S. emanating from the Moscow attack.

Russia's Federal Security Service, the main domestic security and counter-terrorism agency, said 40 people were killed and more than 100 were wounded in the attack at Crocus City Hall, a large music hall on Moscow's western edge.

The assailants threw explosives, triggering the massive blaze at the hall, which can accommodate 6,000, according to Russian news outlets. Video from outside showed the building on fire, with a huge cloud of smoke rising through the night sky. The street was lit up by the blinking blue lights of dozens of firetrucks, ambulances and other emergency vehicles.

The attack took place as crowds gathered for a performance by the famous Russian rock band Picnic. Russian news reports said concertgoers were being evacuated, but that an unknown number could have been trapped by the blaze.

The prosecutor's office said several men in combat fatigues entered the concert hall and fired on concertgoers.

Repeated volleys of gunfire could be heard in videos posted by Russian media and on Telegram channels. One showed two men with rifles moving through the venue. Another showed a man inside the auditorium and saying the assailants had set it on fire, as gunshots rang out incessantly in the background.

Other videos showed up to four attackers, armed with assault rifles and wearing caps, who were shooting at screaming people at point-blank range.

Guards at the concert hall didn't have guns, and some could have been killed at the start of the attack, Russian media reported. It wasn't immediately clear what happened to the assailants, but some Russian news outlets suggested that they fled before special forces and riot police arrived.

Russian authorities said security has been tightened at Moscow's airports, railway stations and the capital's sprawling subway system. Moscow's mayor canceled all mass gatherings, and theaters and museums shut for the weekend. Other Russian regions also tightened security.

The Kremlin hasn't blamed anyone for the attack, but some Russian lawmakers were quick to accuse Ukraine of being behind it. Hours before the attack, the Russian military launched a sweeping barrage on Ukraine's power system, crippling the country's biggest hydroelectric plant and other energy facilities and leaving more than a million people without electricity.

John Kirby, a spokesman for the White House National Security Council, said Friday that he couldn't yet speak about all the details but that "the images are just horrible. And just hard to watch."

"Our thoughts are going to be with the victims of this terrible, terrible shooting attack," Kirby said. "There are some moms and dads and brothers and sisters and sons and daughters who haven't gotten the news yet. This is going to be a tough day."

The attack followed a statement issued earlier this month by the U.S. Embassy in Moscow that urged Americans to avoid crowded places in the Russian capital in view of "imminent" plans by extremists to target large gatherings in Moscow, a warning that was repeated by several other Western embassies.

Asked about the embassy's notice issued on March 7, Kirby referred the question to the State Department, adding: "I don't think that was related to this specific attack."

Responding to a question about whether Washington had any prior information about the assault, Kirby responded: "I'm not aware of any advance knowledge that we had of this terrible attack."

Russia was shaken by a series of deadly terror attacks in the early 2000s during the fighting with separatists in the Russian province of Chechnya.

In October 2002, Chechen militants took about 800 people hostage at a Moscow theater. Two days later, Russian special forces stormed the building, and 129 hostages and 41 Chechen fighters died, most of them from the effects of narcotic gas Russian forces used to subdue the attackers.

And in September 2004, about 30 Chechen militants seized a school in Beslan in southern Russia, taking hundreds of hostages. The siege ended in a bloodbath two days later and more than 330 people, about half of them children, were killed.

CBS News' David Martin, Andy Triay and Olivia Gazis contributed to this report.

In:
• Terrorism
• Russia