UN Secretary-General Antonio Guterres was "shocked" by Sudan's removal of special envoy Volker Perthes, the UN said on Saturday.

Guterres received the letter on Friday from top Sudanese military official Abdel-Fattah Burhan, UN spokesperson Stephane Dujarric said.

"The Secretary-General is shocked by the letter he received this [Friday] morning," Dujarric said. "The Secretary-General is proud of the work done by Volker Perthes and reaffirms his full confidence in his Special Representative."

What do we know about the letter?

No copy of the letter has been published by the UN or the Sudanese army.

Burhan said that the UN had become a "source of negative repercussions," according to Saudi Arabia-based broadcaster Al Hadath.

Sudan's top military official accused Perthes, a diplomat born in the western German city of Duisburg, of practicing "misinformation in his reports," Al Hadath said.

The Associated Press cited an anonymous Sudanese military official as saying that Burhan's letter asked Guterres to replace the UN's special envoy to Khartoum. According to the official, Burhan accused Perthes of "being partisan."

Perthes was appointed to the position in 2021.

Burhan's letter comes after the envoy accused Sudan's warring factions of disregarding the laws of war by attacking homes and civilian infrastructure.

On Monday, Perthes warned of "ethnicization" of the conflict, with the fighting rekindling tensions between the Sudan's various communities.

Last year, Burhan accused the envoy of "exceeding the U.N. mission's mandate and blatant interference in Sudanese affairs" and threatened to expel him from the country.

What is the conflict in Sudan?

Sudan has been rocked by fighting between the country's military under Burhan and the paramilitary Rapid Support Forces (RSF), led by Mohamed Hamdan Daglo, since April 15.

The two rival military figures had been allies in the country's last coup, in October 2021, which ousted leaders charged with ushering in a transition towards democracy after the fall of strongman Omar al-Bashir in 2020.

Roughly 1,800 people have died in the conflict, the Armed Conflict Location & Event Data Project (ACLED) said.

According to the UN, over a million people have been internally displaced within Sudan and at least 300,000 people have fled to neighboring countries. UN-affiliated organizations have repeatedly warned the conflict is exacerbating already-rampant issues like extreme poverty and malnutrition in the country.

The two parties agreed to a one-week cease-fire which is due to expire Monday night. A series of such short-term truces have been agreed since the outbreak of fighting, with almost none of them holding. This time, again, reports of fighting have continued daily despite the supposed cease-fire. 

sdi/msh (AP, AFP, Lusa)