Most of the people buried in a mass grave discovered in the eastern Ukrainian city of Izium are civilians, Ukraine’s police chief said on Friday, based on a preliminary estimate. Earlier, Ukrainian authorities said they had found a mass grave containing 440 bodies in Izium, a former Russian frontline stronghold, and said this was proof of war crimes carried out by the invaders. Russia has not publicly commented on the matter. Its forces fled Izium during a major Ukrainian counter-offensive that retook most of the northeastern Kharkiv region in the past week. Asked if the Izium site contained m…