A U.S. satellite monitoring group has released images of suspected mass graves in Sudan's Southern Kordofan state.

The Satellite Sentinel Project says it has identified three excavated areas consistent with mass graves in Kadugli.

According to the group, witnesses say Sudan's armed forces and Arab militias have systematically killed suspected supporters of the newly independent South Sudan.

The Satellite Sentinel Project is calling for a full-scale investigation into violence in the region.

Fighting between Khartoum's army and pro-southern elements broke out in the area on June 5. Activists say Sudan's military is targeting the state's ethnic Nuba people, many of whom backed the south during a 21-year civil war.

The United Nations says an estimated 73,000 people have been displaced by the fighting.