A rights group says Sudanese government forces are killing and raping civilians in the restive border state of Blue Nile.

The Enough Project renewed its call Tuesday for an investigation into alleged atrocities in the state, where Sudan's government has been fighting rebels since September.

The U.S.-based rights group, which is backed by movie star George Clooney, says its report is based on interviews conducted in late October with Blue Nile refugees in Ethiopia.

The group quotes refugees who say soldiers chased down civilians in the town of Um Darfa and in the words of one refugee, “slaughtered” them. Another refugee said pro-government militias captured and raped some women in the town.

The refugees said they believed they were targeted because of their black skin.

The reports can not be independently confirmed, as Sudan has blocked aid agencies from operating in Blue Nile or in Southern Kordofan, where the government is also fighting rebels.

Both states are on the border of South Sudan, which broke away from Sudan in July.

The United Nations has previously said there is strong evidence of Sudanese government atrocities in the border area, including mass killings, arbitrary detentions, kidnappings, and attacks on churches.

On Monday, a Sudanese official said hundreds of rebels in Southern Kordofan had been killed during a clash with government forces.

Southern Kordofan governor Ahmed Haroun said the violence erupted after insurgents attacked the Teludi. Haroun said the rebels were backed by South Sudan.

Blue Nile and Southern Kordofan were battlegrounds during Sudan's 21-year north-south civil war, and fighters in both states sided with the south.

Sudan and South Sudan have yet to settle disputes over borders and oil revenue stemming from the south's independence. Fighting broke out earlier this year in another area on the border, the oil-rich Abyei region.