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ISIS has claimed responsibility for an attack at a popular concert venue complex near Moscow Friday that left at least 40 dead and more than 100 wounded after assailants stormed the venue with guns and incendiary devices.

The terror group took responsibility for the attack in a short statement published by ISIS-affiliated news agency Amaq on Telegram on Friday. The group did not provide evidence to support the claim.

Video footage from the site of the attack, the Crocus City Hall concert venue, shows the vast complex, which is home to both the music hall and a shopping center, on fire with smoke billowing into the air. State-run RIA Novosti reported the armed individuals “opened fire with automatic weapons” and “threw a grenade or an incendiary bomb, which started a fire.” They then “allegedly fled in a white Renault car,” the news agency said.

State media Russia 24 reported the roof on the venue has partially collapsed.

The attack unfolded before the music group Picnic was set to perform, according to Russia 24. The band’s manager told state media that the performers were unharmed.

The Russia Prosecutor General’s Office said: “Unidentified people in camouflage broke into Crocus City Hall and started shooting before the start of the concert,” according to TASS.

Video footage showed panic as the attack unfolded, with crowds of people huddling together, screaming and ducking behind cushioned seats as gunshots started echoing in the vast hall.

Footage geolocated by CNN shows an armed individual starting at least one fire inside the venue. The individual is seen carrying something in their hand and, as they walk off-screen, a bright flash of light from a large flame is seen in the video.

Regional governor Andrey Vorobyov said everything was being done to save people in what is now the deadliest terror attack on Moscow in decades. A SWAT team was called to the area and more than 70 ambulance teams and doctors were assisting victims.

One hundred and fifteen people have been hospitalized, including five children, the Russian Health Ministry told TASS. Sixty people are in a “serious condition.”

On Friday night, Moscow City Duma Chairman Alexey Shaposhnikov called on Moscow residents to donate blood to help treat victims, saying that “this is a matter of life and death for dozens of people.”

Shaposhnikov listed several blood center facilities in the Moscow area that will accept donors throughout the weekend.

Around 100 people were evacuated from the building by firefighters, TASS reported. Rescuers are still working to get people off the roof, according to the Main Directorate of the Ministry of Emergency Situations of the Russian Federation.

Moscow Mayor Sergei Sobyanin called the attack a “terrible tragedy.”

“Today a terrible tragedy occurred in the Crocus City center. My condolences to the loved ones of the victims. I gave orders to provide all necessary assistance to everyone who suffered during the incident,” Sobyanin said in a statement.

Sobyanin said on Telegram that he was canceling all sports, cultural and other public events in Moscow this weekend.

According to the Kremlin, Russian President Vladimir Putin was informed about the attack and is being kept updated on measures on the ground.

Earlier this month, the US embassy in Russia said it was “monitoring reports that extremists have imminent plans to target large gatherings in Moscow,” including concerts. The embassy warned US citizens to avoid large gatherings.

In a speech Tuesday to Russia’s federal security agency, Putin called the embassy’s warnings about potential terror attacks in Moscow “provocative,” saying “these actions resemble outright blackmail and the intention to intimidate and destabilize our society.”

The US embassy in Moscow on Friday said it was “aware of reports of an ongoing terrorist incident at Crocus City Hall” and advised US citizens not to travel to Russia.

Ukraine, which has been embroiled in a war with Russia for more than two years, denied having any involvement in the attack.

“Ukraine has never resorted to the use of terrorist methods,” Ukrainian presidential adviser Mykhailo Podolyak wrote, in part, in a post on X. He said he believed Russia would use the attack to justify the ongoing conflict and scale up operations as part of “military propaganda” in Ukraine.

United Nations Secretary-General Antonio Guterres late Friday condemned “in the strongest possible terms today’s terrorist attack” according to a statement released by his deputy spokesperson, Farhan Haq.

“The Secretary-General conveys his deep condolences to the bereaved families and the people and the Government of the Russian Federation. He wishes those injured a speedy recovery,” the statement said

This is a developing story and will be updated.

CNN’s Eva Rothenberg and Hannah Strange contributed to this reporting.