More than 100 people have been killed in such attacks on villages near Nyala since January, the High Commissioner said in a report produced together with the UN Mission in Sudan (UNMIS).
It documents violations of international human rights law during an ongoing dispute between members of the Tarjum and Rizeigat Abbala communities in Bulbul area, noting that thousands of people were also displaced and property destroyed.
"The Office [OHCHR] is seriously concerned that to date no effective action has been taken by the government to prevent the attacks or bring the perpetrators to justice," the report noted.
It singles out the involvement of the Sudanese Border Intelligence Guards in attacks by the Rizeigat Abbala on the Tarjum that started in January and continued in March. "In all instances, witnesses described hundreds of heavily armed attackers, many of whom were identified as Border Intelligence personnel," the report said.
Most of the attackers were dressed in green or beige khaki uniforms and accompanied by machine gun-equipped Border Intelligence vehicles. 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 found inside.
They then systematically looted items of value, particularly livestock. In most cases, they also burned large sections of the settlements, the report said.
The report makes several recommendations to the Sudanese government, urging it to investigate all reports of violations and bring perpetrators to justice, and to take measures to avert the threat of further attacks on civilians. It also calls, among other recommendations, for police deployment to protect civilians.
On 16 May, UNMIS warned that continuing violence was threatening humanitarian activities in Darfur. "Incidents of road banditry and fighting between the warring factions continue to disrupt long-term planning," UNMIS spokesperson Radhia Achouri said in Khartoum.
Citing North Darfur state, she warned: "If the situation does not improve, the NGOs' suspension of activities could also affect the populations in Kutum Rural, thus leaving 165,000 people without food assistance at the beginning of the hungry season."
According to Achouri, the continuous stream of new internally displaced persons because of the violence was seriously straining several camps, and services and space are running out.