At least 40 people were killed and 145 wounded on Friday when gunmen opened fire with automatic weapons on concertgoers near Moscow. Isis claimed responsibility for the attack.
Several gunmen dressed in camouflage sprayed bullets at a crowd waiting to see a rock gig at the Crocus City Hall.
Video from the scene showed the gunmen firing indiscriminately at screaming people as they tried to flee.
Explosions were also heard from the venue, whose roof collapsed following a fire outbreak, with pictures showing flames and thick black smoke billowing into the sky.
“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 authorities said they managed to evacuate 100 people hiding in the basement.
The country’s national guard said it was hunting for the attackers, whose identity was yet to be verified.
Isis later claimed responsibility for the attack on its Telegram channel. A statement from the group read: “Islamic State fighters attacked a large gathering of Christians in the city of Krasnogorsk on the outskirts of the Russian capital, Moscow, killing and wounding hundreds and causing great destruction to the place before they withdrew to their bases safely.”
It was not immediately clear exactly how many attackers were involved and what happened to them. Reports said that at least four people were involved.
Russia changed the course of the Syrian civil war by intervening in 2015, supporting President Bashar al-Assad against the opposition and Isis. The group has claimed deadly attacks across the Middle East, Afghanistan, Pakistan, Iran, Europe, the Philippines and Sri Lanka.
Russian politicians and security services referred to the incident as a terrorist attack while it appeared to still be ongoing and launched an investigation.
The attack targeted the large music venue on Moscow’s western edge, according to Russia’s Federal Security Service, the main domestic security and counterterrorism agency, which provided the figures on the dead and wounded.
The assailants threw explosives, triggering the massive blaze at the hall, which can accommodate 6,000, according to Russian news outlets.
Video from outside showed the building on fire, with a huge cloud of smoke rising through the night sky.
The street was lit up by the blinking blue lights of dozens of firetrucks, ambulances and other emergency vehicles, as several helicopters buzzed overhead to dump water on the blaze.
The attack took place as crowds gathered for a performance by the famous Russian rock band Picnic.
Russian news reports said concertgoers were being evacuated, but that an unknown number could have been trapped by the blaze.
The prosecutor’s office said several men in combat fatigues entered the concert hall and fired on concertgoers.
Repeated volleys of gunfire could be heard in videos posted by Russian media and on Telegram channels.
One showed two men with rifles moving through the venue. Another showed a man inside the auditorium as gunshots rang out incessantly in the background.
Other videos showed up to four attackers, armed with assault rifles and wearing caps, who were screaming at people.
Guards at the concert hall didn’t have guns, and some could have been killed at the start of the attack, Russian media reported.
Some Russian news outlets suggested that the assailants fled before special forces and riot police arrived.
As the blaze continued to rage late into the night, statements of outrage, shock and support to those affected streamed in from around the world.
Some commentators on Russian social media questioned how authorities, who relentlessly surveil and pressure Kremlin critics, failed to identify the threat and prevent the attack.
Russian authorities said security has been tightened at Moscow’s airports, railway stations and the capital’s sprawling subway system.
The Kremlin didn’t immediately blame anyone for the attack, but some Russian lawmakers were quick to accuse Ukraine of being behind it and called for ramping up strikes.
Hours before the attack, the Russian military launched a sweeping barrage on Ukraine’s power system, crippling the country’s biggest hydroelectric plant and other energy facilities and leaving more than a million people without electricity.
Dmitry Medvedev, deputy head of Russia’s Security Council, said that if Kyiv’s involvement in the attack on the concert hall is proven, all those involved “must be tracked down and killed without mercy, including officials of the state that committed such outrage”.
Mykhailo Podolyak, an adviser to Ukrainian president Volodymyr Zelenskyy, denied Ukraine’s involvement in the concert hall attack.
“Ukraine has never resorted to the use of terrorist methods,” he posted on X. “Everything in this war will be decided only on the battlefield.”
Two weeks ago, the US embassy in Russia warned that “extremists” had imminent plans for an attack in Moscow. The embassy issued its warning several hours after the FSB said it had foiled an attack on a Moscow synagogue by an Isis cell.
John Kirby, spokesperson for the White House National Security Council, said that he couldn’t yet speak about all the details but that “the images are just horrible. And just hard to watch.”
“Our thoughts are going to be with the victims of this terrible, terrible shooting attack,” Mr Kirby said.
“There are some moms and dads and brothers and sisters and sons and daughters who haven’t gotten the news yet. This is going to be a tough day.”
Emily Foster is a globe-trotting journalist based in the UK. Her articles offer readers a global perspective on international events, exploring complex geopolitical issues and providing a nuanced view of the world’s most pressing challenges.