The Satellite Sentinel Project has released images of what it says are mass graves "consistent with allegations that the Sudan Armed Forces and northern militias have killed civilians."
The satellite images show three large, dark areas side by side, in the south capital of South Kordofan.
"They show evidence consistent with an alleged mass grave identified by at least two eyewitnesses in the vicinity of Kadugli town," SSP director of operations Nathaniel Raymond said.
"They show the presence of white vehicles, including alleged dump trucks identified by multiple eyewitnesses as being Sudan Armed Forces vehicles used in house-to-house searches for civilians, who are allegedly being killed when found," he added.
The human rights group said each of the three excavations are about 90 feet long and 20 feet wide.
The SSP uses both on-the-ground reports and satellite images in its analysis.
There are few details about the situation in Sudan, since the government severely limits access to the region.
Activists have called for the United States and the international community to intervene.
Violence has been widespread in Sudan recently, especially after this year's election that granted South Sudan independence from the North.
*Originally aired on July 15, 2011.