The Berlin office of Navi Pillay had said yesterday that a grave of 75 bodies was found in Bentiu, Unity State. Later the office revised that figure to 34 bodies and 75 people feared missing.
The UN mission in South Sudan said the erroneous report was an inflation of a "skirmish" in which 15 people were killed.
UNMISS said it is still deeply concerned about extra-judicial killings and is investigating those reports.