Army spokesman Nabil Abdallah said in a statement that forces in North Kordofan state had "managed to reopen the road to El-Obeid and merge" with soldiers east of the city.

El-Obeid -- the heart of Sudan's Kordofan region -- sits at a crucial crossroads connecting the capital Khartoum to the country's western region of Darfur, which the RSF has all but conquered.

"El-Obeid's strategic importance, especially its airport and its position linking western Sudan with the centre and south, makes today's operation one of the most critical militarily," a military source told AFP, requesting anonymity because they are not authorised to brief the media.

Sudan's finance minister in the army-aligned government described breaking the siege as a turning point in the conflict.

"This strategic victory represents a qualitative shift in the path of a larger triumph," Gibril Ibrahim said in a post on Facebook.

He added that it is also "a significant step towards lifting the siege" on North Darfur's besieged capital of El-Fasher which has been under RSF siege since May.

Reopening the routes would allow the delivery of essential food and medicine to the Kordofan region, he added.

Witnesses told AFP thousands of residents took to the streets of El-Obeid to celebrate.

The war, which has pitted army chief Abdel Fattah al-Burhan against the RSF for nearly two years, has killed tens of thousands, uprooted over 12 million and created the world's largest hunger crisis.

Famine has been declared in three displacement camps in the western region of Darfur as well as parts of the Nuba Mountains in the south.

It is expected to spread to five more areas by May, according to a UN-backed assessment.