Sudan's army killed a key rebel leader from the Darfur region Sunday, state media reported, 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 in west Wadbanda, North Kordofan," the official Sudan News Agency (SUNA) said.
Ibrahim headed the Justice and Equality Movement (JEM), the most heavily armed group in the Darfur region.
The report of his death 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 Khartoum.
JEM spokesman Gibril Adam Bilal said then that 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.
On the official Sudan TV channel, Saad said Sunday that government forces "clashed directly" with Ibrahim's troops, killing him and "a group of his leaders" as Ibrahim was on his way to South Sudan.
The South became independent in July following an overwhelming vote to separate after a two-decade civil war. Sudanese troops have been battling rebels on the poorly-defined southern border, with each country accusing the other of supporting rebels within their territories.
The governor of North Kordofan, also on Sudan TV, said rebel vehicles were seen burning after the clash in west Wadbanda, in the border region between his state and South Darfur.
In 2008, more than 222 people were killed when JEM guerrillas drove about 1,000 kilometres across the desert to Omdurman, just across the River Nile from the presidential palace on the Khartoum side.
Government troops repulsed them after heavy clashes and later sentenced dozens of rebels to death for their role in the assault.
In July, the government signed the Doha Document for Peace in Darfur with the Liberation and Justice Movement, an alliance of rebel splinter factions.
Darfur's main armed groups -- JEM and factions of the Sudan Liberation Army headed by Minni Minnawi and Abdelwahid Nur -- did not sign the deal.
Instead, last month they, along with the SPLM-North rebel group, ratified documents forming the new Sudanese Revolutionary Front dedicated to "popular uprising and armed rebellion" against the National Congress Party regime in Khartoum.
According to the United Nations at least 300,000 people have been killed in Darfur since 2003 when fighting broke out between non-Arab rebels and the Arab-dominated Khartoum regime.
The government puts the death toll at 10,000.
UN officials say 1.9 million people are internally displaced and still living in camps in Darfur, with about 80,000 newly displaced by fighting this year.
Six people including President Bashir are being sought or are before the International Criminal Court in The Hague for crimes in Darfur.