Ukraine says it will investigate footage that Moscow alleges shows Ukrainian forces executing more than 10 Russian troops who may have been trying to surrender.
The two countries have accused each other of war crimes, after videos appeared to show one of the alleged Russian soldiers refusing to lay down his weapon and opening fire, before a larger flurry of gunfire erupted.
Here's what we know about the footage, the allegations of war crimes and the promised investigations.
When and where was the footage recorded?
It wasn't clear exactly when the videos were filmed, but the Reuters news agency said it verified that the footage was recorded in the town of Makiivka, in the Luhansk region of eastern Ukraine.
Reporters from the agency said a courtyard, buildings and a fence from the scene of the footage matched recent satellite imagery.
Andrey Marochko, a man who identified himself as a Russian officer based in the Luhansk region, claimed on the social media platform Telegram that the footage was filmed in Makiivka.
Russian media gave the same location, as did the New York Times.
The videos appear to be taken outdoors, in the yard of a damaged building which also contains a damaged swing set, a damaged toy car and what appears to be a sandpit.
It was also unclear who filmed the videos, but an armed person wearing a yellow arm band — a colour used by Ukrainian forces to identify themselves — appeared to hold the camera at one stage in the footage.
Ukrainian forces claimed to have regained control of Makiivka in recent weeks, but reports suggest the town may still be under Russian control.
What does the footage appear to show?
The longest section of the footage shows a group of about 10 men in full military gear, some lying on the ground and others emerging from a small outbuilding with their hands raised, apparently unarmed.
Under orders shouted by someone off-camera, they join the others already on the ground.
Some of the men are wearing red bands on their lower legs. Red or white markers are sometimes worn by Russian and Russia-aligned troops to identify themselves as members of the Kremlin's forces.
The video also features other men watching them, shown to be armed and wearing flashes of yellow on their arms, legs and helmets.
A man with a yellow armband appears to hold the camera while another, also with a yellow armband, is shown lying on the ground with a machine gun and ammunition.
At least two other armed men wearing bits of yellow also appear to be watching the apparent surrender.
In the last few seconds of the video, a man emerges from behind the outbuilding, and appears to be armed.
Amid what sounds like sustained gunfire, the video becomes too blurred to see what happened next. It cuts off a few seconds later.
A separate, eight-second snippet without sound reportedly shows those final moments slowed down. As he emerges, the apparently armed man appears to raise a rifle and open fire, with the muzzle of the gun emitting puffs of smoke.
Another separate snippet of video, seemingly shot with a drone and not featuring any soldiers with yellow armbands, appears to show men lying motionless in what appear to be pools of blood.
The videos do not conclusively reveal exactly how or why the alleged deaths occurred.
The footage also has several edit points, so does not show every moment which leads up to the images of motionless bodies.
How did the footage come to light?
An edited and blurred version of drone footage from the alleged scene was released by the Ukrainian Ministry of Defence on November 16, claiming that Ukraine was back in control of Makiivka.
Videos were also posted on Russian Telegram channels and relayed on other social media.
Russia last week accused Ukrainian soldiers of executing more than 10 Russian prisoners of war, citing a video circulating on Russian social media.
Kremlin spokesman Dmitry Peskov told reporters: "There is no doubt that Russia itself will be looking for the perpetrators of this crime. They must be found and punished."
What are the war crime allegations made by both sides?
Both Moscow and Kyiv have accused each other of committing war crimes during the incident in question.
The Russians claim Ukrainian forces shot unarmed Russian prisoners of war, while Ukraine's commissioner for human rights, Dmytro Lubinets, claims Russian soldiers opened fire during the act of surrendering.
He said the videos appeared to show "a staged capture" where Russian forces were not really surrendering.
"From separate pieces of the video of the incident involving Russian soldiers in the Luhansk region it can be concluded that, using a staged capture, the Russians committed a war crime — they opened fire on soldiers of the Armed Forces of Ukraine," Mr Lubinets wrote on Telegram.
"In this case, the Russian military personnel cannot be considered prisoners of war, but are fighting and committing perfidy.
"Returning fire is not a war crime. On the contrary, those who want to use the protection of international law for murder must be punished," he added.
The Kremlin said on Monday, November 21, that it would bring to justice those responsible for the alleged execution of Russian prisoners of war in Ukraine, and that it would do everything possible to draw attention to what it has called a war crime.
The Russian defence ministry said the footage showed "the deliberate and methodical murder of more than 10 immobilised Russian serviceman by degenerate Ukrainian soldiers".
Also on Monday, Ukrainian President Volodymyr Zelenskyy again repeated his calls for NATO nations and other allies to recognise Russia as a terrorist state.
Who is investigating the incident?
Ukraine's Deputy Prime Minister for European and Euro-Atlantic integration, Olha Stefanishyna, said Ukrainian authorities would investigate the footage, and it was "very unlikely" that the edited snippets showed what Moscow claimed.
Ms Stefanishyna said Ukrainian forces were "absolutely not interested in the execution of anybody" and were under direct orders to take "as many prisoners of war as we can" so they could be swapped in prisoner exchanges with Russia.
"Every potential executed Russian soldier is some Ukrainian that is not able to be exchanged, so the spirit and logic is not there," she said.
Russia's Investigative Committee, which investigates serious crimes, said it had opened a criminal case into the execution of "at least 11 unarmed Russian servicemen".
Russian Foreign Ministry spokesperson Maria Zakharova said the video was "further evidence of the crimes of Ukrainian neo-Nazis and Ukraine's flagrant violation of international humanitarian law, including the Geneva Conventions".
"We demand that international organisations condemn this egregious crime and conduct a thorough investigation into it," Ms Zakharova said.
Washington's envoy for war crimes said on Monday that the United States was monitoring allegations of Ukrainian forces executing Russian troops, and said all parties should face consequences if they commit abuses in the conflict.
The United Nations' Human Rights Monitoring Mission in Ukraine has called for further investigation, telling the Associated Press that "all such allegations should be properly and promptly investigated by respective authorities".
Asked if Ukraine will allow an international investigation, Ms Stefanishyna said: "We will see. No problem with that."
Other allegations of war crimes during the war in Ukraine
Both Russian and Ukrainian forces have been accused of war crimes since Moscow began its invasion of Ukraine in late February, but reports of crimes allegedly perpetrated by Russian forces vastly outnumbered ones allegedly carried out by Ukrainians.
The UN, rights groups and journalists have found that during their nearly nine-month invasion, Russian forces have committed widespread abuses and alleged war crimes.
Matilda Bogner, who heads the UN Monitoring Mission in Ukraine, said earlier this week that Ukrainian troops were suspected of abuses against people who weren't in combat.
"We have received credible allegations of summary executions of persons hors de combat (out of combat), and several cases of torture and ill-treatment, reportedly committed by members of the Ukrainian armed forces," she said.
Ms Bogner said the mistreatment of Ukrainian prisoners by Russians was "fairly systematic", but the mistreatment of Russian prisoners by Ukrainian forces was "not systematic".
ABC/Wires
