Russia observed a national day of mourning on Sunday as investigators said the death toll from Friday's massacre in a concert hall near Moscow had risen to at least 137, making it the deadliest attack in Europe to have been claimed by the Islamic State (IS) group.
Russian President Vladimir Putin has vowed to punish those behind the "barbaric terrorist attack", saying four gunmen trying to flee to Ukraine had been arrested.
Kyiv has strongly denied any connection, with Ukrainian President Volodymyr Zelensky accusing Putin of trying to shift the blame onto them.
Russian officials on Sunday said the confirmed death toll from the attack on the Crocus City Hall concert venue had risen to at least 137, including three children.
They warned that the number was expected to rise further, with more than 100 wounded in hospital.
Read moreIn pictures: Gunmen open fire in deadly attack on Moscow concert hall
The emergency situations ministry has so far named 29 of the victims, a devastating blaze at the site having complicated the process of identification.
The ministry posted a video Sunday of heavy equipment arriving at the scene to dismantle damaged structures and clear debris.
Russia's Investigative Committee, which probes major crimes, said guns and rounds of ammunition had been found both at the concert hall and in a car that was used by the suspected gunmen to flee the scene.
'Barbaric'
Camouflaged gunmen stormed the concert hall in Moscow's northern suburb of Krasnogorsk on Friday evening, before setting fire to the building.
The Islamic State group wrote on Telegram the next day that the attack was "carried out by four IS fighters armed with machine guns, a pistol, knives and firebombs," as part of "the raging war" with "countries fighting Islam".
Putin, in his first public remarks on the attack, made no reference to a statement by the IS group claiming responsibility.
"Terrorists, murderers, non-humans ... have only one unenviable fate: retribution and oblivion," he said in his televised address Saturday.
Calling the attack a "barbaric, terrorist act", he said "all four direct perpetrators ... all those who shot and killed people, have been found and detained".
Russian television showed security services interrogating four bloodied men, who spoke Russian with an accent, on a road in the western Bryansk region, which borders both Ukraine and Belarus.
"They tried to escape and were travelling towards Ukraine, where, according to preliminary data, a window was prepared for them on the Ukrainian side to cross the state border," said Putin.
Zelensky, in his evening address Saturday, dismissed the suggestion that Kyiv had been involved.
"What happened yesterday in Moscow is obvious," he said. "Putin and the other scum are just trying to blame it on someone else."
Victims died from gunshot wounds, smoke inhalation
Putin declared Sunday a day of national mourning.
And he promised: "All the perpetrators, organisers and those who ordered this crime will be justly and inevitably punished."
The interior ministry said all four of the suspected gunmen were foreign nationals.
Russian Telegram channels -- including those with links to the security services -- said they were from Tajikistan, a country that borders Afghanistan and where the IS group is active.
Tajikistan's foreign ministry told Russia's TASS news agency it was in close contact with Moscow over the matter.
The IS group had first claimed responsibility for the attack on Friday night, repeating its claim again on Saturday.
Witnesses of the attack filmed the gunmen from the upper floors as they walked through the stalls shooting people, sharing the footage on social media.
Then "the terrorists used a flammable liquid to set fire to the concert hall's premises, where spectators were located, including wounded," the Investigative Committee said.
Investigators said people died both from gunshot wounds and smoke inhalation after a fire engulfed the 6,000-seater venue.
Investigators said a man who jumped on one of the gunmen as he was shooting at the concert-goers, "immobilising" him and thus "saving the lives of people around him" would receive an award.
US warning dismissed
In Washington, the White House issued a statement condemning the attack and describing the IS group group as a "common terrorist enemy that must be defeated everywhere".
Just three days earlier, Putin had publicly dismissed a US warning of an "imminent" attack in Moscow as propaganda designed to scare Russian citizens.
The US embassy in Russia had warned on March 7 that "extremists have imminent plans to target large gatherings in Moscow, to include concerts", advising caution over the following 48 hours.
Washington said after the attack it had also shared details directly with Moscow.
But speaking to FSB chiefs last Tuesday, Putin had called it a "provocative" statement and "outright blackmail... to intimidate and destabilise our society".
On Sunday, the White House reiterated its earlier assertion that Ukraine had "no involvement whatsoever" in the concert hall attack near Moscow.
"ISIS bears sole responsibility for this attack. There was no Ukrainian involvement whatsoever," said White House National Security Council spokeswoman Adrienne Watson, using an acronym for the IS group.
(FRANCE 24 with AFP)
