Possible Mass Graves Near Mariupol Shown In Satellite Images

Ukrainian officials have accused Russia of burying thousands of civilians near Mariupol, with new satellite images suggesting the presence of mass graves. These graves could contain up to 9000 victims. The mayor of Mariupol claims that Russia is attempting to cover up alleged war crimes by burying the bodies outside the city. However, Newsie has not been able to independently verify these reports.

What does the Mariupol mayor accuse Russia of trying to cover up?

What has Newsie been unable to do regarding the reports of mass graves?