In a post Thursday on Telegram, Petro Andriushchenko, an adviser to the mayor of Mariupol, wrote: "As a result of a long search and identification of places of mass burial of dead Mariupol residents, we established the fact of arrangement and mass burial of the dead Mariupol residents in the village of Manhush."

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Andriushchenko — who is not in Mariupol but has served as a clearinghouse for information from inside the besieged city — posted the coordinates on Telegram, saying Russian forces had dug several mass graves, each measuring about 30 meters (around 100 feet), in Manhush, a town around 12 miles (about 19 kilometers) to the west of Mariupol.

"Trucks carry in the bodies of the dead, in fact, simply dumping them on the embankment," he said. "This is direct evidence of war crimes and attempts to cover them up."