NEW YORK: United Nations Secretary General Antonio Guterres has said he is `shocked` by a letter from Sudanese army chief Abdel Fattah al-Burhan, reportedly requesting the replacement of special envoy Volker Perthes amid a brutal war with paramilitaries.

Guterres `is proud of the work done by Volker Perthes and reaffirms his full confidence in his Special Representative`, a statement from UN spokesperson Stephane Dujarric said.

`The secretary-general is shocked by the letter he received from General Al-Burhan,` currently at war with his former deputy Mohamed Hamdan Dag10, who commands RSF.

Neither the army nor the UN released official copies of Burhan`s letter, which reportedly requested the dismissal of Perthes as Guterres` envoy to Sudan.

Perthes is currently in NewYork, where he briefed the Security Council on the situation in Sudan earlier this week. There is no information on when he is due back in Sudan, where authorities have not given out visas to foreign nationals since the war started.

Khartoum was calmer on Saturday morning as a seven-day ceasefire appeared to reduce fighting between two rival military factions although it has not yet provided the promised humanitarian relief to millions trapped in the capital.

A truce signed by the two fighting parties Sudan`s army and a paramilitary group called the Rapid Support Forces aimed to secure safe passage for humanitarian aid and lead to wider talks sponsored by the US and Saudi Arabia.

Witnesses said Khartoum was calmer although sporadic clashes were reported overnight.

Gulf broadcaster Al-Arabiyareported some clashes in northwestern Khartoum and southern Omdurman.

The conflict, which erupted on April 15, has killed at least 730 civilians and caused 1.3 millionSudanese to leave their homes.

Aid agencies say they have struggled to get the bureaucratic and security guarantees to transport aid and staff to Khartoum and other hot zones.-Agencies