The United Nations has accused Sudanese security forces of killing more than 100 people in machine gun attacks on villages in South Darfur over a three-month period.
In a report covering the period from January to March, UN High Commissioner for Human Rights Louise Arbour called on the government to carry out an independent investigation into the attacks near Nyala.
"In all instances, witnesses described hundreds of heavily armed attackers, many of who were identified as Border Intelligence personnel," the report said.
"During all the incidents, attackers fired indiscriminately from the outskirts of the settlements with heavy machine guns and rocket propelled grenades, before entering the settlements and shooting men."
The border intelligence guards, often recruited from the local population, is a generally secretive unit but "known to be under the control of Military Intelligence", the report said.
It said some attackers had left behind military identification cards.
The violence, in an area known as Bulbul, began with a land dispute between two ethnic Arab groups, the Rizeigat Abbala and Tarjum, according to the report. It said Sudanese forces had sided with the Rizeigat Abbala in carrying out the attacks.
At least 200,000 people have been killed and more than two million displaced since 2003 in an ethnic and political conflict triggered by a rebellion in Darfur. Rebels are fighting government troops and their Janjaweed militia allies.