Sudanese and U.N. officials say the United Nations secretary-general was “shocked” by a letter from Sudan’s army chief demanding the removal of the U.N. envoy to the country

Sources in Sudan’s foreign ministry told Al Jazeera Volker Perthes will not be allowed back into the war-torn country.

The fighting across Sudan has killed more than 1,800 people, according to the Armed Conflict Location and Event Data Project. The United Nations says more than a million people have been displaced within Sudan,

Sudanese army chief Abdel Fattah al-Burhan has accused UN special envoy Volker Perthes of stoking a brutal conflict with paramilitaries, the latest in a series of apparent moves to bolster his war effort.