The African Union said on Wednesday it would not recognise a "so-called parallel government" in Sudan, urging its members to follow suit.
A bitter two-year civil war in Sudan has pitted the government against the Rapid Support Forces (RSF), which announced it was forming a government and appointed a prime minister on Saturday.
The AU's Peace and Security Council "called on all AU Member States and the international community to reject the fragmentation of Sudan and not recognise the so-called 'parallel government' which has serious consequences on the peace efforts and the existential future of the country," it said in a statement.
Sudan is split, with the army controlling the north, east and centre, having recently retaken the capital Khartoum, while the RSF holds most of Darfur and parts of Kordofan, where recent attacks have killed hundreds according to local rights groups.