Sudan's army killed a key rebel leader from the Darfur region, state media reported Sunday, three days after anti-government forces said they had begun advancing on the capital Khartoum.

"The Sudanese army announce that they killed Khalil Ibrahim in fighting today west of Wadbanda in North Kordofan," the official Sudan News Agency (SUNA) said.

Ibrahim headed the Justice and Equality Movement, the most heavily armed group in the Darfur region.

The report could not be independently confirmed.

On Saturday SUNA, quoting army spokesman Sawarmi Khaled Saad, said the military was combing the North Kordofan-North Darfur border area after JEM "attacked civilians" and targeted local leaders while looting their property in the Umm-Gozain, Goz Abyadh and Aramal areas.

Saad gave no casualty figures.

The JEM announced on Thursday through its London-based spokesman that its forces were advancing from Darfur eastward towards the capital Khartoum.

JEM spokesman Gibril Adam Bilal said the group had reached En Nahud, about 120 kilometres (75 miles) east of Darfur in North Kordofan, on a mission to topple the regime led by President Omar al-Bashir.