MOSCOW -- Assailants burst into a large concert hall in Moscow on Friday and sprayed the crowd with gunfire, killing more than 60 people, injuring more than 100 and setting fire to the venue.
The Islamic State group claimed responsibility for the attack in a statement posted on affiliated channels on social media. A U.S. intelligence official told The Associated Press that U.S. intelligence agencies had learned that the group's branch in Afghanistan was planning an attack in Moscow and shared the information with Russian officials.
It wasn't immediately clear what happened to the attackers after the raid, which state investigators were investigating as terrorism.
The attack, which left the concert hall in flames with a collapsing roof, was the deadliest in Russia in years and came as the country's war in Ukraine dragged into a third year. Moscow Mayor Sergei Sobyanin called the raid a "huge tragedy."
The Kremlin said Putin was informed minutes after the assailants burst into Crocus City Hall, a large music venue on Moscow's western edge that can accommodate 6,200 people.
The attack took place as crowds gathered for a performance by the Russian rock band Picnic. The Investigative Committee, the top state criminal investigation agency, reported early today that more than 60 people were killed. Health authorities released a list of 145 injured -- 115 of them hospitalized, including five children.
Some Russian news reports suggested that more victims could have been trapped by the blaze that broke out after the assailants threw explosives.
Video 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 as fire helicopters buzzed overhead to dump water on the blaze that took hours to contain.
The prosecutor's office said several men in combat fatigues entered the concert hall and fired on concertgoers.
Dave Primov, who was in the hall during the attack, described panic and chaos when the shooting began.
"There were volleys of gunfire," Primov told the AP. "We all got up and tried to move toward the aisles. People began to panic, started to run and collided with each other. Some fell down and others trampled on them."
Videos posted by Russian media and on messaging app channels showed men toting assault rifles shooting screaming people at point-blank range. One video showed a man in the auditorium saying the assailants had set it on fire as gunshots rang out incessantly.
Guards at the concert hall didn't have guns, and some could have been killed at the start of the attack, Russian media reported. Some Russian news outlets suggested that the assailants fled before special forces and riot police arrived. Reports said police patrols were looking for several vehicles the attackers could have used to escape.
In a statement posted by its Aamaq news agency, the Islamic State group said it attacked a large gathering of "Christians" in Krasnogorsk on Moscow's outskirts, killing and wounding hundreds. It was not immediately possible to verify the authenticity of the claim.
However, U.S. intelligence officials confirmed the claim by the Islamic State group's branch based in Afghanistan that it was responsible for the Moscow attack, a U.S. official told the AP.
The official said U.S. intelligence agencies had gathered information in recent weeks that the IS branch was planning an attack in Moscow. He said U.S. officials privately shared the intelligence earlier this month with Russian officials. The official was briefed on the matter but was not authorized to publicly discuss the intelligence information and spoke to the AP on condition of anonymity.
On Friday, statements of anger, shock and support for those affected by the concert hall attack streamed in from around the world.
Some commentators on Russian social media questioned how authorities, who relentlessly surveil and pressure Kremlin critics, failed to identify the threat and prevent the attack.
Russian officials said security was 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 closed for the weekend. Other Russian regions also tightened security.
The Kremlin didn't immediately blame anyone for the attack, but some Russian lawmakers were quick to accuse Ukraine and called for ramping up strikes.
Dmitry Medvedev, deputy head of Russia's Security Council, said that if Ukraine involvement was proven, all those involved "must be tracked down and killed without mercy, including officials of the state that committed such outrage."
Mykhailo Podolyak, an adviser to Ukrainian President Volodymyr Zelenskyy, denied Ukraine involvement.
"Ukraine has never resorted to the use of terrorist methods," he posted on X. "Everything in this war will be decided only on the battlefield."
John Kirby, spokesperson for the White House National Security Council, said he couldn't yet speak about the details but "the images are just horrible and just hard to watch."
Friday's attack followed a statement earlier this month by the U.S. Embassy in Moscow that urged Americans to avoid crowded places in view of "imminent" plans by extremists to target large gatherings in the Russian capital, including concerts. The warning was repeated by several other Western embassies.
National Security Council spokesperson Adrienne Watson said Friday that the U.S. government had information about a planned attack in Moscow, prompting the State Department advisory to Americans. The U.S. government shared the information with Russian authorities in accordance with its longstanding "duty to warn" policy, Watson said.
Putin, who extended his grip on Russia for another six years in this week's presidential vote after a sweeping crackdown on dissent, denounced the Western warnings as an attempt to intimidate Russians. "All that resembles open blackmail and an attempt to frighten and destabilize our society," he said earlier this week.
Information for this article was contributed by Michael Balsamo of The Associated Press.
Russian Rosguardia (National Guard) servicemen secure an area near the Crocus City Hall on the western edge of Moscow, Russia, Friday, March 22, 2024. Several gunmen have burst into a big concert hall in Moscow and fired automatic weapons at the crowd, injuring an unspecified number of people and setting a massive blaze in an apparent terror attack days after President Vladimir Putin cemented his grip on the country in a highly orchestrated electoral landslide. (AP Photo/Vitaly Smolnikov)
A medic stands near ambulances parked outside the burning building of the Crocus City Hall on the western edge of Moscow, Russia, Friday, March 22, 2024. Several gunmen have burst into a big concert hall in Moscow and fired automatic weapons at the crowd, injuring an unspecified number of people and setting a massive blaze in an apparent terror attack days after President Vladimir Putin cemented his grip on the country in a highly orchestrated electoral landslide. (AP Photo/Vitaly Smolnikov)
A man speaks to journalists as a massive blaze seen over the Crocus City Hall on the western edge of Moscow, Russia, Friday, March 22, 2024. Several gunmen have burst into a big concert hall in Moscow and fired automatic weapons at the crowd, injuring an unspecified number of people and setting a massive blaze in an apparent terror attack days after President Vladimir Putin cemented his grip on the country in a highly orchestrated electoral landslide. (AP Photo/Dmitry Serebryakov)
A Russian Rosguardia (National Guard) servicemen secures an area as a massive blaze seen over the Crocus City Hall on the western edge of Moscow, Russia, Friday, March 22, 2024. Several gunmen have burst into a big concert hall in Moscow and fired automatic weapons at the crowd, injuring an unspecified number of people and setting a massive blaze in an apparent terror attack days after President Vladimir Putin cemented his grip on the country in a highly orchestrated electoral landslide. (AP Photo/Dmitry Serebryakov)
Russian Rosguardia (National Guard) servicemen help a man to leave an area near the Crocus City Hall on the western edge of Moscow, Russia, Friday, March 22, 2024. Several gunmen have burst into a big concert hall in Moscow and fired automatic weapons at the crowd, injuring an unspecified number of people and setting a massive blaze in an apparent terror attack days after President Vladimir Putin cemented his grip on the country in a highly orchestrated electoral landslide. (AP Photo/Vitaly Smolnikov)
Ambulances parked near the burning building of the Crocus City Hall on the western edge of Moscow, Russia, Friday, March 22, 2024. Several gunmen have burst into a big concert hall in Moscow and fired automatic weapons at the crowd, injuring an unspecified number of people and setting a massive blaze in an apparent terror attack days after President Vladimir Putin cemented his grip on the country in a highly orchestrated electoral landslide. (AP Photo/Dmitry Serebryakov)
A massive blaze is seen over the Crocus City Hall on the western edge of Moscow, Russia, Friday, March 22, 2024. Several gunmen have burst into a big concert hall in Moscow and fired automatic weapons at the crowd, injuring an unspecified number of people and setting a massive blaze in an apparent terror attack days after President Vladimir Putin cemented his grip on the country in a highly orchestrated electoral landslide. (AP Photo/Dmitry Serebryakov)
A Russian National Guard serviceman secures an area Friday as a huge blaze is seen over the Crocus City Hall on the western edge of Moscow. Several gunmen burst into the concert hall in Moscow and fired automatic weapons at the crowd, killing 60 people and injuring more than 100 others while also setting a large blaze. (AP)