MOSCOW -- Camouflage-clad gunmen opened fire at concertgoers with automatic weapons on Friday, killing at least 60 people and injuring 145 more in an attack claimed by Islamic State militants.

In the deadliest attack in Russia since the 2004 Beslan school siege, gunmen sprayed civilians with bullets just before Soviet-era rock group "Picnic" was to perform to a full house at the 6,200-seat the Crocus City Hall just west of Moscow.

Verified video showed people taking their seats in the hall then rushing for the exits as repeated gunfire echoed above screams. Other video showed men shooting at groups of people. Some victims lay motionless in pools of blood.

"Suddenly there were bangs behind us - shots. A burst of firing - I do not know what," one witness who asked not to be named told Reuters.

"A stampede began, everyone ran to the escalator," the witness said. "Everyone was screaming, everyone was running."

Russian investigators said the death toll was more than 60. Health officials said about 145 people were wounded, of which about 60 were in critical condition.

In the 2004 Beslan school siege, Islamist militants took more than 1,000 people, including hundreds of children, hostage.

Crocus City Hall attack Russia

Islamic State

Islamic State, the militant group that once sought control over swathes of Iraq and Syria, claimed responsibility for the attack, the group's Amaq agency said on Telegram.

A grainy picture was published by some Russian media of two of the alleged attackers in a white car.

The fate of the attackers was unclear as firefighters battled a massive blaze and emergency services evacuated hundreds of people while parts of the venue's roof collapsed.

Islamic State said its fighters attacked on the outskirts of Moscow, "killing and wounding hundreds and causing great destruction to the place before they withdrew to their bases safely." The statement gave no further detail.

The United States has intelligence confirming Islamic State's claim of responsibility for the shooting, a U.S. official said on Friday. The official said Washington had warned Moscow in recent weeks of the possibility of an attack.

"We did warn the Russians appropriately," said the official, speaking on condition of anonymity, without providing any additional details.

Russia has yet to say who it thinks is responsible.

The attack on Crocus City Hall, about 20 km from the Kremlin, comes just two weeks after the U.S. embassy in Russia warned that "extremists" had imminent plans for an attack in Moscow.

Hours before the embassy warning, the FSB said it had foiled an attack on a Moscow synagogue by Islamic State's affiliate in Afghanistan, known as ISIS-Khorasan or ISIS-K, and seeks a caliphate across Afghanistan, Pakistan, Turkmenistan, Tajikistan, Uzbekistan and Iran.

Putin changed the course of the Syrian civil war by intervening in 2015, supporting President Bashar al-Assad against the opposition and Islamic State.

"ISIS-K has been fixated on Russia for the past two years, frequently criticizing Putin in its propaganda," said Colin Clarke of the Soufan Center.

The broader Islamic State group has claimed deadly attacks across the Middle East, Afghanistan, Pakistan, Iran, Europe, the Philippines and Sri Lanka.

Russian Foreign Ministry spokeswoman Maria Zakharova said it was a "bloody terrorist attack" that the entire world should condemn.

The United States, European and Arab powers and many former Soviet republics expressed shock and sent their condolences. Ukrainian presidential adviser Mykhailo Podolyak denied any Ukrainian involvement.

The United Nations Security Council condemned what it called a "heinous and cowardly terrorist attack."

Security tightened

Putin, who was on Sunday re-elected for a new six-year term, sent thousands of troops into Ukraine in 2022 and has repeatedly warned that various powers - including countries in the West - are seeking to sow chaos inside Russia.

Crocus City Hall attack Russia

Putin was informed in the first minutes of the attack and is regularly being updated, the Kremlin said.

"The president constantly receives information about what is happening and about the measures being taken through all relevant services. The head of state gave all the necessary instructions," Kremlin spokesperson Dmitry Peskov said.

After the attack, Russia tightened security at airports, transport hubs and across the capital - a vast urban area of over 21 million people. All large-scale public events were canceled across the country.

"A terrible tragedy occurred in the shopping center Crocus City today," Moscow Mayor Sergei Sobyanin said. "I am sorry for the loved ones of the victims."

The White House said that images of the shooting were hard to watch, while Germany's foreign ministry called the images "horrific."

"Our thoughts obviously are going to be with the victims of this terrible, terrible shooting attack," White House spokesman John Kirby said.