The paramilitary Rapid Support Forces (RSF) and anti-government rebels captured the city of Al Kurmuk in Sudan's southern Blue Nile state on Tuesday.
The RSF and the Sudan People's Liberation Army-North (SPLA-N) struck an alliance soon after the civil war between the army and the paramilitary broke out nearly three years ago.
The SPLA-N has been fighting successive Sudanese governments for decades. It controls large areas of territory in the southern Kordofan and Blue Nile regions. The RSF controls the entire Darfur region, an area roughly the size of France, as well as parts of Kordofan.
The army controls the capital, Khartoum, as well as the central, eastern and northern regions of the vast Afro-Arab nation.
The SPLA-N on Tuesday called on residents of the Blue Nile state capital of Damazin, 130km from Al Kurmuk, to stay at home and avoid military sites in the city. Damazin is home to the army's 4th Infantry Division.
"Your forces are closing in on Damazin," the group said in a statement in which residents were also told that no harm would come to them. Earlier on Tuesday, the RSF posted a video online of its fighters and those of the SPLA-N celebrating the capture of Al Kurmuk.
Blue Nile state is an agricultural region that has about 60 per cent of the country's forests. It has seen increasing fighting between the army and the SPLA-N in recent weeks. Both Al Kurmuk and Damazin control vital roads leading north and east towards the border with Ethiopia.
Sudan's war is essentially a power struggle between army chief Gen Abdel Fattah Al Burhan, also Sudan's de facto ruler, and RSF commander Gen Mohamed Dagalo. Tens of thousands of people have died in the civil war and it has created the world's largest humanitarian and displacement crises, with about 25 million – nearly half the population – facing hunger, and at least 12 million having fled their homes.
