Updates with comments and background
The Russian Defence Ministry on Friday accused Kyiv of executing at least 10 prisoners of war in what Moscow said constituted a "war crime," the latest allegation of abuses after nearly nine months of fighting in Ukraine.
Moscow's claims come after the UN this week published a report saying prisoners of war on both sides had been subjected to torture and ill-treatment.
"No one will be able to paint the deliberate and methodical murder of more than 10 restrained Russian soldiers ... who were shot in the head, as a 'tragic exception,'" the ministry said in a statement.
The statement came as videos circulated on Russian-language social media that purport to show the bodies of Russian servicemen who had surrendered and were then killed.
One video shows soldiers apparently surrendering to several military personnel in camouflage and wearing yellow armbands. The soldiers who are giving themselves up lie down on the ground in the debris-filled backyard of a house.
The video then abruptly cuts off as shots are heard.
Another video filmed from above shows the bodies of around a dozen people surrounded by apparent blood stains.
It has not been possible to independently verify the authenticity of the videos and the Russian Defence Ministry did not say when the footage was shot.
Russia's Human Rights Council said the alleged executions took place in the village of Makiivka, in the Luhansk region of eastern Ukraine, which the Ukrainian army said it recaptured this week.
"We will ask for a reaction and an investigation from the international community," Human Rights Council Chairman Valery Fadeyev said on social media.
The ministry claimed that the videos represent "new evidence of a massacre of unarmed Russian prisoners of war by Ukrainian military personnel," and said that "the brutal murder of Russian prisoners of war is not the first and not the only war crime" committed by Ukrainian forces.
Moscow also accused Ukraine's Western allies of turning a blind eye to alleged abuses carried out by the Ukrainian military.
Kyiv would be held responsible for "every prisoner tortured and killed," the statement read.
There was no immediate response to the allegations from Ukrainian officials.
The allegations from Moscow come a day after a Dutch court sentenced two Russian men and a Ukrainian to life imprisonment over the downing of Malaysia Airlines flight MH17 over Ukraine in 2014.