UNITED NATIONS (AP) — Sudanese paramilitary forces are encircling the only capital they haven’t captured in the western Darfur region, the United Nations said Friday, warning that an attack would have “devastating consequences” for the city’s 800,000 inhabitants.

At the same time, the U.N. said, the rival Sudanese Armed Forces “appear to be positioning themselves.”

U.N. Secretary-General António Guterres again called on the paramilitary Rapid Support Forces and government forces to refrain from fighting in the North Darfur area around its capital, El Fasher, U.N. spokesman Stephane Dujarric said.

The year-old war in Sudan between rival generals from the paramilitary and government forces who are vying for power has sparked “a crisis of epic proportions,” U.N. political chief Rosemary DiCarlo said last Friday. It has been fueled by weapons from foreign supporters who continue to flout U.N. sanctions aimed at helping end the conflict, she said, stressing that “This is illegal, it is immoral, and it must stop.”