STORY: In an interview at his presidential office, he told Reuters an investigation was underway with international assistance and that there was evidence of war crimes in areas occupied for months by Russian invaders.
"All this is there. Investigative commissions with international partners, joint investigative commissions," Zelenskiy said.
"Our prosecutors are also working with international ones. There is some evidence, and assessments are being conducted, Ukrainian and international, and this is very important for us, for the world to recognize this."
Bodies with their hands tied were found at a mass burial site in Izium after Ukrainian forces recaptured the city in northeastern Ukraine, the regional governor said on Friday.
Earlier, Ukrainian officials said they had found hundreds of corpses of mainly civilians in woodland.
Russia denies targeting civilians and has said in the past that accusations of human rights abuses are a smear campaign.