Sudan's army-aligned government on Saturday spurned an invitation to an east African summit and rebuked the United Nations for engaging with the commander of rival paramilitary forces.

Nine months after war broke out between the regular army and the paramilitary Rapid Support Forces, the army has been losing territory while paramilitary leader Mohamed Hamdan Daglo has been touring African capitals in a boost to his diplomatic standing.

Rejecting the invitation from east African bloc IGAD to a summit in Uganda on January 18 also to be attended by Daglo, Sudan's transitional sovereign council, headed by army chief Abdel Fattah al-Burhan, insisted: "The events in Sudan are an internal matter."

The bloc has repeatedly attempted to mediate between Sudan's warring generals, but its efforts have been cold-shouldered by Burhan's government.

In contrast, Daglo, fresh from a tour of six African capitals, said on X, formerly Twitter, that he had accepted the invitation from IGAD and would be attending the summit in Uganda.

Sudan's foreign ministry said inviting Daglo was a "flagrant violation" and "destroys the credibility of IGAD" as an institution.

"Not only has IGAD been silent as a grave over the atrocities of the terrorist militia, it has also sought to grant the militia legitimacy by inviting it to a meeting attended only by member state heads of state and government," it charged.

Burhan has reacted angrily to Daglo's growing diplomatic status, accusing African leaders who hosted him on his recent tour of complicity in atrocities against Sudanese civilians.

Analysts say the army chief is growing more and more isolated diplomatically, as his troops fail to halt RSF advances.

- UN call -

The war has killed more than 13,000 people, according to a conservative estimate by the Armed Conflict Location & Event Data project. Some 7.5 million civilians have fled the fighting, according to UN figures.

Both sides have been accused of war crimes, including the indiscriminate shelling of residential areas, torture and arbitrary detention of civilians.

The RSF has also specifically been accused of ethnically-motivated mass killings, rampant looting and the use of rape as a weapon of war.

In the eastern city of Port Sudan, which is now home to Burhan's government, acting foreign minister Ali al-Sadiq told newly arrived UN envoy Ramtane Lamamra that Sudan "rejects" a recent contact between UN chief Antonio Guterres and Daglo, according to a statement carried by official news agency SUNA.

Sadiq said he informed Lamamra that the UN chief's phone call on Thursday served to "legitimise" Daglo, "the leader of a movement that has committed horrific violations that have been condemned by some UN institutions as well as the majority of the international community."

Lamamra was named Guterres's envoy for Sudan, after the termination of the UN mission to the country last month at the request of Burhan's government.