Ukraine is investigating more than 25,000 alleged war crimes cases since the Russian invasion five months ago.
Yuriy Bilousov, head of the war crimes unit of the attorney general’s office, said 135 people had been charged, but only 15 of them were detained and 120 were still at large.
He told Reuters that since Vladimir Putin’s invasion on February 24, 13 cases had been brought to the court and seven judgments had been handed down.
In May, a 21-year-old captured Russian soldier became the first person to be convicted in a war crimes trial in Ukraine. He was sentenced to life in prison for killing an unarmed civilian.
“We are sometimes asked why these … low-level officials are being prosecuted. It’s just because they are here,” Mr Bilusov said.
“If the generals were there, we could capture [them], we will definitely sue the general. “
There were reports of civilians killed in the streets of Butcha, some with their hands tied, and satellite images showed what appeared to be a mass grave in the town.
U.S. President Joe Biden called Putin a “war criminal” and Ukrainian President Vladimir Zelensky called the situation in Butcha an act of genocide.
The first independent investigation into allegations that Russia violated humanitarian law in Ukraine, released in April, found evidence of multiple war crimes.
A preliminary report from the Organization for Security and Cooperation in Europe (OSCE) found that the bombing of a children’s hospital and theatre in the besieged port city of Mariupol constituted a war crime, as did the forcible deportation of thousands of Ukrainians to Russia.
Investigators said there were “credible reports” of civilians being detained by Russian forces and subjected to ill-treatment that amounted to torture.