Sudan's army leader, Abdel Fattah al-Burhan, has accused United Nations Special Envoy Volker Perthes of stoking a brutal conflict with paramilitaries in a letter in which he called for replacing Perthes.

Commenting on the accusation, the United Nations chief Antonio Guterres said he was "shocked" by al-Burhan's letter, which called for "the nomination of a replacement" to Perthes and accused him of committing "fraud and disinformation" in clearing the way for a political process, which broke down into six weeks of catastrophic clashes.

Al-Burhan and his former deputy, Mohammed Hamdan Dagalo, who leads the paramilitary Rapid Support Forces, were supposed to meet for UN-mediated talks on April 15, the day the clashes erupted in Khartoum.

The gathering attempted to restart a transition to civilian administration that had been stalled since 2021 when al-Burhan and Dagalo took control in a coup before splitting off. As their rivalry grew worse, the world community attempted to persuade them to strike an agreement on the incorporation of Dagalo's RSF into the regular army.

Perthes and the UN mission in Sudan, which he leads, have been the subject of repeated protests since late last year, with thousands of military and Islamist supporters accusing Perthes of "foreign intervention" and demanding his expulsion. 

Since the beginning of the clashes, similar protests have taken place in the eastern city of Port Sudan.

Perthes had kept his "optimism" and claimed the clashes took him "by surprise".

Al-Burhan accused Perthes of bias in the letter and of failing to respect "national sovereignty".

Perthes, he said, painted an inaccurate picture of "consensus" in his UN reports, and "without these signs of encouragement, the rebel leader Dagalo would not have launched his military operations."

The conflict has so far killed more than 1,800 people, according to the latest figures from the Armed Conflict Location and Event Data Project.

Meanwhile, the chaos has left millions hunkering down in their homes to find shelters from the bullets and roaming looters amid power blackouts and shortages of water, food, medicines, and other staples.

Fighting between Sudan's rival generals has displaced over one million people within the country since it began on April 15, as per the International Organization for Migration.

'We cannot look away'

George Clooney, the actor and longtime advocate for human rights in Sudan, urged the international community to "up its focus". 

"We cannot look away," he said.

Guterres said he was "shocked by the letter" from al-Burhan and "proud of the work done by Volker Perthes," reaffirming his full confidence in his Special Representative in a statement sent by UN spokesperson Stephane Dujarric.

The US State Department voiced its "strong support" for Perthes and its "concern" over al-Burhan's letter calling for his resignation.

It is worth noting that a one-week ceasefire -- which was mediated by the US and Saudi Arabia -- ends Monday night. 

The two nations urged the rival generals to resume dialogue on extending the ceasefire to aid in the "delivery of urgently needed humanitarian assistance" to civilians, the official Saudi Press Agency reported.

The mediators stated in a joint statement on Friday that they "noted improved respect for the agreement," but that there was still "isolated gunfire in Khartoum."

Al-Burhan dismissed Dagalo as his deputy in the governing Sovereign Council last week, replacing him with former rebel commander Malik Agar.

Even after rumors of al-Burhan's letter surfaced, Agar stated that he had discussed "ways to resolve the crisis and end the war" with Perthes.

The army is likewise looking to beef up its ranks. The Defense Ministry ordered "army pensioners" and reservists to report to command units on Friday, which the RSF described as a "dangerous decision".

Perthes is now in New York, where he briefed the Security Council on Sudan on Monday. Those accountable, he says, are "the two generals at war," in response to those who "accuse the UN."

Read next: Sudan: A borderless conflict