Horrific video footage shows Ukrainian soldiers surrendering before being brutally killed by the Russian invaders.
The footage, obtained by CNN, was filmed in August near the city of Pokrovsk, where Russian soldiers have made advances in recent weeks.
Three surrendering Ukrainians were killed in the video after they were overrun by the Russians.
A Ukrainian defence intelligence source claimed there have been 15 cases similar to this one since November.
Ukraine’s prosecutor general, Andriy Kostin, said his office is investigating at least 28 such incidents since the war began in February 2022.
He added: “If prisoners of war surrender, if they show that they surrender, if they are without weapons in their hands, then summary execution is a war crime.”
Mr Kostin said Kyiv has “an opportunity to claim that such policy could be elevated to crimes against humanity. This policy is orchestrated by Kremlin. It’s an order of specific commanders.”
Other cases similar to the incident in Pokrovsk include one in Toretsk, where a unit claimed it had filmed Russian troops shooting Ukrainian soldiers who were emerging from a basement.
Russian soldiers have been placed on trial over allegations of executing Ukrainian troops, including one in the Zaporizhzhia region.
One incident in Zaporizhzhia involved three Ukrainians who were lying on the floor face down.
A Russian commander says: “Take them f**king down, f***king zero them, zero them.”
His subordinate replied: “Got it, copy.”
The commander added: “Once you zero them, report back.”
The Russians then opened fire at the surrendering Ukrainians.
A UN investigative source told CNN: “The killings are war crimes individually…and together could amount to crimes against humanity.”
Russia has not commented on the execution allegations.