Six months of war between Sudan’s military and a powerful paramilitary group has killed up to 9,000 people and created “one of the worst humanitarian nightmares in recent history,” the United Nations humanitarian chief said.

Sudan has been engulfed in chaos since mid-April, when simmering tensions between military chief Gen. Abdel-Fattah Burhan and the commander of the paramilitary Rapid Support Forces, Gen. Mohamed Hamdan Dagalo, exploded into open warfare.