Ukrainian President Volodymyr Zelensky says investigators have uncovered more than 400 war crimes in areas of Kherson abandoned by retreating Russian forces.
Mr Zielinski said the bodies of civilians and soldiers had been found.
JEE News is unable to confirm these allegations. Moscow denies that its troops deliberately target civilians.
Meanwhile, Ukrainian authorities imposed an overnight curfew and banned travel in and out of Kherson.
“In the Kherson region, the Russian army left behind atrocities like in other areas of our country, where it was able to enter,” Mr Zelensky said in his nightly video address.
“We will find every murderer and bring them to justice. Of course.”
Since the start of the war, mass graves have been found in areas including Bucha, Ezeum and Mariupol. Ukraine has alleged that Russian soldiers are behind the atrocities.
A UN commission said last month that war crimes had been committed in Ukraine and that Russian forces were responsible for the “vast majority” of human rights abuses at the start of the invasion.
Kherson was the only regional capital held by Russia after the invasion of Ukraine in February.
The region, along with three others, was declared part of Russia by President Vladimir Putin at a ceremony in the Kremlin in September.
But the city of Kherson was liberated by Ukrainian troops on Friday. Crowds of flag-waving Ukrainians greeted Kyiv’s soldiers with hugs and kisses.
Officials have returned to run Kherson’s administration after the withdrawal of some 30,000 Russian occupation troops.
Ukrainians see it as a major national victory and a humiliation for the Kremlin, on par with the Russian withdrawal from the Kyiv suburbs in March.
It is feared that some Russian soldiers may have stayed behind in disguise, while accomplices who aided the Russians during the occupation may be prosecuted.
Mr Zelinsky said Russian soldiers and mercenaries who were “left behind in the area” had been detained and the process of neutralizing the saboteurs was ongoing.
He said Ukrainian forces were working to restore internet and television connections, while electricity and water supplies would be restored “as soon as possible”.
