Moscow, March 23: The Islamic State has claimed responsibility for the massive attack on concert hall in the Russian capital that left at least 40 people dead and over 100 wounded, CNN reported.

A group of armed men stormed into Crocus City Hall concert venue in Moscow and opened fire and detonated explosives among the crowd on Friday.

The terror group took responsibility for the attack in a short statement published by ISIS-affiliated news agency Amaq on Telegram on Friday. However, ISIS has not provided any evidence to support the claim. Moscow Concert Hall Shooting: Multiple Deaths Feared After Heavy Firing at Entertainment Venue in Russia's Kransogorsk, Videos Surface.

Video footage from the site of the attack, the Crocus City Hall concert venue on fire with smoke billowing into the air. It showed crowds of people huddling together, screaming and ducking behind cushioned seats as gunshots started echoing in the vast hall.

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. Moscow Concert Hall Shooting: At Least 60 Dead, Over 145 Injured After Heavy Firing at Entertainment Venue in Russia's Kransogorsk; Islamic State Group Claims Responsibility (Watch Video).

The claim by the Islamic State was also confirmed by US officials shortly afterwards, the New York Times reported.

The US officials said they had privately apprised Russian officials about the intelligence pointing to an impending attack, the New York Times reported.

The United States collected intelligence in March that Islamic State-Khorasan, known as ISIS-K, the branch of the group based in Afghanistan, had been planning an attack on Moscow, according to officials. ISIS members have been active in Russia, a US official said.

After a period of relative quiet, the Islamic State has been trying to increase its external attacks, according to US counterterrorism officials. Most of those plots in Europe have been thwarted, prompting assessments that the group has diminished capabilities.

The attack on Friday in Moscow, followed by the one in Iran in January, could prompt a reassessment of its ability to strike outside its home territory, according to the NYT.

"ISIS-K has been fixated on Russia for the past two years," frequently criticising President Vladimir Putin in its propaganda, said Colin P Clarke, a counterterrorism analyst at the Soufan Group, a security consulting firm based in New York.

"ISIS-K accuses the Kremlin of having Muslim blood in its hands, referencing Moscow's interventions in Afghanistan, Chechnya and Syria," he added.

The US officials said that in addition to publicly warning on March 7 about a possible attack, they had privately told Russian officials about the intelligence pointing to an impending attack, the New York Times reported. But, it is not clear how much information Washington gave to the Moscow officials beyond what was in the public warning.

Earlier, the US had also warned Iran of a possible attack ahead of twin bombings in January that killed at least 103 people and wounded 211 others at a memorial service for Iran's former top general, Qassim Suleimani, who was killed by a U.S. drone strike four years before. ISIS-K claimed responsibility for that attack too.

Meanwhile, 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.

115 people have been hospitalised, including five children, the Russian Health Ministry told TASS. 60 people are in a 'serious condition'.

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," as reported by CNN.

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.

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