More than 60 people have been killed and over 145 injured after armed gunmen opened fire at concertgoers at Crocus City Hall located in the outskirts of Moscow, Russia.

At least 60 among those injured in the attack, which took place on Friday, are in critical condition.

The attackers targeted people moments before Soviet-era rock group “Picnic” was to perform to a full house at the 6,200-seat the Crocus City Hall located West of the Russian capital.

The terrorist attack, for which militant group Daesh has taken responsibility, is the deadliest terror incident in Russia since the 2004 Beslan school siege wherein militants had taken more than 1,000 people hostage.

“Suddenly there were bangs behind us — shots. A burst of firing — I do not know what,” one witness, who asked not to be identified by name, told Reuters.

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

Russian President Vladimir Putin was being updated by security chiefs about the situation, including from Alexander Bortnikov, the head of the Federal Security Service (FSB), the Kremlin said.

Russian investigators published pictures of a Kalashnikov automatic weapon, vests with multiple spare magazines and bags of spent bullet casings.

Meanwhile, in a statement, Daesh said its fighters attacked on the outskirts of Moscow, “killing and wounding hundreds” […] before they withdrew to their bases safely.”

However, Moscow has yet to say who it thinks is responsible.

The United States has intelligence confirming Daesh’s claim of responsibility for the shooting, a US official said on Friday. The official said Washington had warned Moscow in recent weeks of the possibility of an attack.

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

The attack on Crocus City Hall, about 20 kilometres (12 miles) from the Kremlin, comes just two weeks after the US embassy in Russia warned that “extremists” had imminent plans for an attack in Moscow.

The US, 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 (UNSC) has also condemned what it called a “heinous and cowardly terrorist attack.”