Russia concert hall death toll rises to 137

Russian investigators said Sunday they had found weapons and ammunition at the Moscow concert hall hit in Friday's attack, as the death toll rose to 137.

"The bodies of 137 people, three of whom are children, have been found at the scene," Russia's Investigative Committee said in a statement, adding that guns and rounds of ammunition had been found both there and in a car that was used by the suspected gunmen to flee the scene.

Russia was observing a National Day of Mourning on Sunday after a massacre in a Moscow concert hall killed more than 130 people, 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.

The whole country is in mourning with those who lost their loved ones in this inhumane tragedy, public television channel Russia 24 said on Sunday morning.