Ukrainian authorities have found a mass grave in the recently liberated eastern town of Lyman and it is unclear how many bodies it holds, regional governor Pavlo Kyrylenko said in an online post on Friday.
Separately, the Ukrinform news agency cited a senior police official as saying the grave contained 180 bodies. Ukrainian troops retook Lyman, in the Donetsk region, from Russian control on Saturday.
Ukrainian authorities have regularly accused Russian troops of committing atrocities in occupied territories, a charge Moscow denies.
Last month the bodies of 436 people were exhumed from a burial site in the northeastern town of Izium after it was liberated. Most appeared to have died violent deaths, local officials said.
Kyrylenko, governor of Donetsk, wrote on Telegram that officials in Lyman had found "a mass grave where, according to local information, there could be both soldiers and civilians. The exact number is yet to be ascertained."
He said a second burial site with 200 graves had also been found, containing the bodies of civilians. It was not clear from his comments how or when they had died.