NEW YORK, NY.- Several camouflage-clad gunmen opened fire at a popular concert venue on the outskirts of Moscow on Friday night, killing about 60 people and wounding more than 100, said the FSB, Russia’s top security agency. That death toll would make it the deadliest attack in the capital region in more than a decade.

As gunshots boomed through the building containing the concert hall, one of the largest and most popular music venues in the Moscow area, fire erupted in the upper floors of the structure, and the blaze intensified after an explosion, the news agency RIA Novosti reported.

The Islamic State group, through an affiliated news agency, claimed responsibility. U.S. security officials, including a senior counterterrorism official, said they believed the attack was carried out by the Islamic State in Khorasan, a branch of the terrorist group that is active in Pakistan, Afghanistan and Iran. They spoke on the condition of anonymity because they were not authorized to discuss the matter publicly.

Multiple videos posted on social media and verified by The New York Times show several people entering Crocus City Hall, a sprawling shopping and entertainment complex in suburban Krasnogorsk, northwest of Moscow, and firing rifles. Other videos show people running past bloodied victims lying on the floor or screaming at the sound of gunshots, while photos show bodies lined up outside the building.

A woman who gave her name only as Marina said in a text message that she was standing in line for a concert outside, in the cold, about 8 p.m. when people without overcoats started running out of the building, saying they had heard shots.

“As soon as I heard automatic rifle shots, I started running, too,” she said.

The state news agency TASS reported that emergency services had dispatched helicopters to try to rescue people from the building’s roof, where flames and smoke could be seen billowing into the night sky. The roof near the concert stage was collapsing around 10 p.m. local time, RIA Novosti reported.

Hours after the mayhem began, the Russian national guard said its officers were still looking for the attackers and evacuating people from the complex. State media agencies reported that there had been up to five perpetrators.

At least 115 people have been hospitalized from the attack on the Moscow concert hall, five of them children, according to the Russian minister of health, Mikhail Murashko. The injured include 60 adult patients in serious condition, the minister said. Another 30 people were treated and released.

Russia’s Investigative Committee, the country’s equivalent to the FBI, said it had opened a criminal case into a terrorist act and dispatched its investigators to the site. RIA Novosti said that a special police unit was working inside the building.

John Kirby, a spokesperson for President Joe Biden’s National Security Council, told reporters that the White House had “no indication at this time that Ukraine or Ukrainians were involved.” Mykhailo Podolyak, a top adviser to Ukraine’s presidential office, said in a video statement that “Ukraine has absolutely nothing to do” with the attack.

On March 7, the U.S. Embassy in Moscow issued a security alert that warned that its personnel were “monitoring reports that extremists have imminent plans to target large gatherings in Moscow, to include concerts.” The statement, which did not say anything about the extremists’ affiliation, warned Americans that an attack could take place in the next 48 hours.

Pro-Kremlin voices seized on the U.S. Embassy’s warning to paint America as trying to scare Russians. On March 19, President Vladimir Putin of Russia called the statement “obvious blackmail” made with “the intention to intimidate and destabilize our society.”

The attack Friday was connected to the March 7 warning, according to U.S. officials briefed on the matter. They added that the United States alerted Russia privately at the time about intelligence it had about Islamic State group activity.

Statements of condolence and outrage came from around the world, including the governments of the United States and other countries that are at odds with Russia. Yulia Navalnaya, the widow of opposition leader Alexei Navalny, who died in a Russian prison last month, said on social media, “All those involved in this crime must be found and brought to justice.”

The attack came on a day when 165 missiles and drones attacked Ukraine, constituting what the U.S. ambassador to Ukraine, Bridget Brink, said was “the largest attack against Ukraine’s energy grid since the start of Russia’s war.”

The shooting occurred minutes before a sold-out performance by veteran rock band Piknik was scheduled to start. The concert hall has 6,200 seats, according to its website.

“At least three people in camouflage burst into the ground floor of Crocus City Hall and opened fire with automatic weapons” and threw incendiary devices, a correspondent for RIA Novosti reported from the scene. “There are definitely wounded.”

In videos filmed inside the concert hall, audience members are heard screaming and seen crouching as repeated gunshots echo outside the hall.

Russia’s emergency service said it had sent 130 vehicles to the scene and three helicopters to drop water on the blaze that gutted the upper floors. By late evening, the fire seemed to have died down considerably.

Shootings are rare in Russia, where the state tightly regulates the possession of firearms. One of the deadliest ones occurred in 2022, when a gunman killed 18 people and wounded 23 others in a school in the town of Izhevsk.

If the figures of 60 dead and more than 100 injured Friday are correct, then the toll is comparable to that of the 2011 suicide bombing at Moscow’s Domodedovo Airport, which killed 37 people, and two coordinated suicide bombings in Moscow subway stations in 2010 that killed 38.

In 2004, 172 people died in a siege at a Moscow theater by Chechen separatists. Police pumped a sedative gas into the theater to incapacitate the attackers, but the gas killed 132 hostages.

The complex where the attack took place Friday was developed by Azerbaijan-born billionaire Aras Agalarov, whose son, Emin, is a famous pop star. Former President Donald Trump held the Miss Universe pageant at the same complex in 2013, and world-famous performers like Eric Clapton, Dua Lipa and Sia have also performed there.

This article originally appeared in The New York Times.