At least 133 people have been killed and more than 100 others injured after gunmen opened fire and set off explosives at a concert hall on the western edge of Moscow.
Here’s what we know so far:
The Russian capital is a sprawling city that is home to some 12 million people.
The Crocus City Hall, which includes a shopping centre and conference venue, lies in suburban Krasnogorsk, about 20km (12 miles) west of the Kremlin and alongside the Moscow ring road.
Opened in 2009, the concert hall is a popular entertainment venue with a capacity for 6,200 people.
Former United States President Donald Trump once held a Miss Universe contest there.
The attack began on Friday evening just as people were taking their seats for a sold-out show by Picnic, a popular rock band from the Soviet era.
As many as five men in combat fatigues entered the concert hall and opened fire on those inside.
Dave Primov, who was in the hall during the attack, described chaotic scenes.
“There were volleys of gunfire,” Primov told The Associated Press news agency. “We all got up and tried to move toward the aisles. People began to panic, started to run and collided with each other. Some fell down and others trampled on them.”
Russian investigators said at least 133 people had been killed, while more than 100 others were injured in one of the worst attacks to hit the country in decades.
The attackers also set off explosives that ignited a huge blaze that at one point covered as much as 12,900 square metres (139,000sq ft), according to Russian news agency Interfax.
Graphic videos posted on social media showed the gunmen firing repeatedly as they entered the building, and shooting people at point-blank range.
Another video showed a man in the auditorium saying the attackers had set it on fire.
Helicopters were brought in to douse the flames from the air, as firefighters battled the blaze from the ground. The fire was eventually brought under control early on Saturday.
The Emergency Situations Ministry said firefighters helped about 100 people escape through the building’s basement, while rescue operations were also launched for people trapped on the roof.
TASS news agency said the band members of Picnic were not harmed and were evacuated safely.
Russia’s Investigative Committee, the top state criminal investigation agency, opened a “terrorist” investigation into the attack and the national guard, Rosgvardia, was among units deployed to search for the gunmen.
Nikolai Patrushev, the secretary of Russia’s security council and a key ally of President Vladimir Putin, has said the Moscow attack shows how serious the threat of terrorism is to Russia, TASS reported.
He added that those who carried out the attack would be held to account.
Russia’s FSB security service has told Putin that 11 people have been detained, including four people directly involved in the attack, Interfax cited the Kremlin as saying.
At least two suspects were arrested in the Bryansk region, some 340km (210 miles) southwest of Moscow, following a car chase, said politician Alexander Khinshtein, citing “preliminary information”. Other suspects fled into a nearby forest and are being pursued, he added.
The Kremlin did not immediately blame anyone for the attack, but some Russian politicians were quick to accuse Ukraine.
Mykhailo Podolyak, an adviser to Ukrainian President Volodymyr Zelenskyy, denied Ukraine’s involvement.
“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.”
Islamic State in Khorasan Province (ISKP), an Afghan affiliate of ISIL (ISIS), claimed responsibility for the attack in a statement posted by its Amaq news agency.
It said its fighters had attacked on the outskirts of Moscow, “killing and wounding hundreds and causing great destruction to the place before they withdrew to their bases safely” and then escaped. The news agency gave no further details.
Russia has reported several incidents involving ISIL this month, with the FSB intelligence agency saying on March 7 it foiled an attack by ISKP on a Moscow synagogue.
The US said it had also warned of the heightened threat posed by “extremists” with imminent plans for an attack on “large gatherings” in Moscow and had shared that finding with the Russians. On Friday night, a US official said Washington had intelligence confirming ISIL’s claim of responsibility for the Crocus City Hall attack.
Experts said the group had opposed Russian President Vladimir Putin in recent years.
“ISIS-K [ISKP] has been fixated on Russia for the past two years, frequently criticising Putin in its propaganda,” said Colin Clarke of the Soufan Center, a Washington-based research group.
Michael Kugelman of the Washington, DC-based Wilson Center said ISKP “sees Russia as being complicit in activities that regularly oppress Muslims”.
Russian President Vladimir Putin said on Saturday that all those responsible for the Moscow attack would be identified and punished.
“All the perpetrators and organisers behind this crime will, inevitably, face a just punishment. Regardless of who they are, and who was directing them, we will identify and punish everyone who was behind this terrorist attack,” he said in an address to the nation.
Putin also claimed the attackers had tried to escape towards Ukraine. He said that preliminary information showed that some people in Ukraine were prepared to let them cross the border from Russia.
Sunday has been declared a national day of mourning, he added.
Earlier, Putin wished a speedy recovery to the wounded victims and conveyed his thanks to doctors who had treated the injured, Russia’s deputy prime minister Tatyana Golikova was quoted as saying by Russian news agencies after meeting with him.<
At least 60 people wounded in the attack are in a serious condition, the Russian Health Ministry said.
Dozens of people lined up outside the Gavrilov Blood Center in Moscow to donate blood needed to treat victims of the attack, Russia’s RIA Novosti news agency reported. The facility is Russia’s largest blood transfusion centre.
In October 2015, an ISIL-planted bomb exploded on a Russian passenger plane over the Sinai desert, killing all 224 people on board, most of them Russians returning from their holidays in Egypt.
The country was also shaken by a series of deadly attacks in the early 2000s.
In September 2004, about 30 Chechen fighters seized a school in Beslan in southern Russia taking hundreds of people hostage. The siege ended in a bloodbath two days later and more than 330 people, about half of them children, were killed.
In October 2002, Chechen fighters stormed a theatre in Moscow taking about 800 people hostage in the auditorium. Russian special forces launched a bid to rescue the captives two days later, by first subduing the attackers with a narcotic gas. Some 41 Chechens died, as well as 129 hostages, mostly from the effects of the gas.
Germany, Afghanistan, Norway, Cuba, Italy, Japan, Venezuela, Israel, the Palestinian Authority and Malaysia are among others who have condemned the attack.
