A U.S.-based group said Thursday it has corroborated U.N. reports and eyewitness accounts claiming that Sudanese government forces committed violence against civilians in the country's Southern Kordofan state earlier this year.

The Satellite Sentinel Project says it has analyzed satellite images and collected field reports that indicate Sudan's Central Reserve Police (CRP) engaged in the unlawful abduction, detention, and extrajudicial killing of civilians in Southern Kordofan beginning in June.

In July, the United Nations said there was “strong evidence” atrocities were being carried out by Sudanese forces in the area, citing “credible reports” of mass killings, arbitrary detentions, kidnappings, aerial bombardment and attacks on churches.

The U.N. blames most of the violence in Southern Kordofan on Sudan's army, police and allied militia.

The U.N. said Sudanese forces harassed the U.N. mission in Sudan with physical assaults, arbitrary arrests, and ill treatment amounting to torture.

Satellite Sentinel Project aerial photographs suggest that the CRP significantly built up a facility near the U.N. mission between June and August of 2011, the time period when government forces were said to be attacking internally displaced persons seeking refuge there.

Fighting between Southern Kordofan's ethnic Nuba rebels, who are seen as supporters of South Sudan, and government forces began just one month before South Sudan split from the north and declared independence.

The Nuba fighters sided with the south during Sudan's 21-year north-south civil war.

Khartoum has repeatedly claimed the South Sudanese military is supporting the rebels in the oil-rich border state, but Juba denies the charges.