STORY: "It's horrifying. It's repugnant. And sadly, it's in keeping with the kind of depravity and the brutality with which Russian forces have been prosecuting this war against Ukraine and the Ukrainian people," Kirby said.
Ukrainian officials said they had found 440 bodies in woodlands near the city of Izium. They said most of the dead were civilians, and that the site proved war crimes had been committed by Russian invaders who occupied the area for months.
The site in Izium, a former Russian front-line stronghold, would be the biggest mass burial found in Europe since the aftermath of the 1990s Balkan wars. Ukrainian forces retook Izium after thousands of Russian troops fled the area, abandoning weapons and ammunition.
Russia denies that its occupation forces have committed atrocities. The head of the pro-Russian administration which abandoned the area last week, Vitaly Ganchev, was quoted by Russia's TASS state news agency as accusing Ukrainian forces of being responsible for killings and trying to blame Moscow.