From my research, this claim appears true. Multiple reports from but not limited to Reuters, the BBC, and the UN all corroborate this story. As I understand, on may 22nd Ukraine release a drone strike, hitting a student dorm in Luhansk, Russia, harboring up to 86 students at the time. Russian reports claim up to 18 students may have been trapped in the rubble at the time of the press releases. Russian Officials claim that there are no relevant military operations in the area, but Ukraine claims no intentional harm to civilians, stating they only wish to recapture previously owned land. In response to this attack, Putin has ordered Moscow to prepare retaliations.
sources
United Nations
British Broadcasting
Company Reuters