Fears have soared in recent days of renewed ethnic slaughter in the Sudanese region of Darfur, where genocidal violence killed as many as 300,000 people two decades ago, with a threatened assault looming over an embattled city already facing famine.

The contest for control of El Fasher, the last city held by Sudan¡¯s military in Darfur, has prompted alarmed warnings from American and United Nations officials who fear mass bloodshed may be imminent. Linda Thomas-Greenfield, the U.S. envoy to the United Nations, told reporters Monday that the city was ¡°on the precipice of a large-scale massacre.¡±

El Fasher is the latest flashpoint in a year-old civil war between Sudan¡¯s military and the Rapid Support Forces (RSF), a powerful paramilitary group the military once nurtured that is now its bitter rival for power. The conflict has devastated one of Africa¡¯s largest countries and created a vast humanitarian crisis U.N. officials say is one of the biggest in decades.