Ukraine has launched an investigation to find Russian soldiers who apparently killed an unarmed Ukrainian prisoner of war, after graphic footage emerged.
"We will find the murderers," President Volodymyr Zelensky said late on Monday.
In the video, the Ukrainian soldier is seen smoking a cigarette in a trench. He says "Glory to Ukraine!" before being shot with automatic weapons.
One military unit has named the soldier as one of its own, but there are conflicting reports about his identity.
In the footage, one of the shooters - believed to be a Russian soldier - is heard saying "die" and using an expletive after the prisoner of war (POW) is shot dead.
The alleged killer or killers - who are not seen in the clip - have not been identified.
The video first emerged on social media on Monday. The BBC has not verified where and when the footage was made, or how the soldier was captured.
The general staff of Ukraine's armed forces said: "The shooting of an unarmed prisoner is a cynical and brazen disregard for the norms of international humanitarian law and the customs of war. This is what worthless murderers do, not warriors.
"The Russian occupiers have once again shown that their main goal in Ukraine is the brutal extermination of Ukrainians."
Russia has not publicly commented on the incident.
In his video address, President Zelensky said "the occupiers" killed "a warrior who bravely said to their faces: 'Glory to Ukraine!'"
"I want us all to respond to his words together, in unity: 'Glory to the Hero! Glory to the Heroes! Glory to Ukraine!'"
Mr Zelensky was referring to a battle cry in Ukraine's military that has become popular among millions of Ukrainians.
Meanwhile, Ukrainian Foreign Minister Dmytro Kuleba tweeted that the footage was "another proof this war is genocidal", and he called for an "immediate investigation" by the International Criminal Court.
And Ukraine's Prosecutor General Andriy Kostin said a criminal investigation had already been opened.
On Tuesday, Ukraine's military named the soldier as Tymofiy Shadura, citing preliminary information.
His unit, the 30th Separate Mechanised Brigade, said he was last seen on 3 February near the eastern city of Bakhmut - the scene of fierce fighting in recent months.
But it added that the identification could only be completed after the body was returned.
Before the soldier was named, Mr Shadura's sister, Olia, said she recognised her brother: "[He] would certainly be capable of standing up to the Russians
