A key rebel group in Sudan's troubled Darfur region said on Thursday it has chosen a one-time university professor to head the movement after his brother, the former leader, was killed last month.

At a two-day meeting in South Kordofan state, the Justice and Equality Movement selected Gibril Ibrahim to replace his brother Khalil, the group's spokesman Gibril Adam Bilal told AFP.

"(The) Justice and Equality Movement held its extraordinary general conference in South Kordofan, attended by 109 people who elected Gibril Ibrahim as the leader," Bilal said by satellite telephone.

The JEM meeting affirmed its commitment to work with other rebel groups "to remove the regime," and endorsed all decisions made by its late leader in previous years, he added.

Gibril Ibrahim trained as an economist and worked as a professor at universities in Khartoum and Saudi Arabia. He has recently been based in London where he served as an adviser to JEM and head of its foreign relations.

JEM announced that his brother Khalil Ibrahim, 54, was killed on December 23 in an air strike, although Sudan's military said the long-time rebel chief was wounded during a clash with government forces in North Kordofan, which adjoins North Darfur state, and died later.

JEM and other Darfur African rebel groups rose up against the Arab-dominated Khartoum government in 2003 and were confronted by state-backed Janjaweed militia in a conflict that shocked the world and led to allegations of genocide.

In 2008, Khalil Ibrahim's forces staged a dramatic march on Khartoum and reached as far Omdurman, just across the Nile river from the presidential palace, before being pushed back.

The United Nations estimates at least 300,000 people have died because of the Darfur conflict, with about 300 killed in deadly armed clashes last year.

The Sudanese government puts the total number killed at 10,000.

Darfur plunged into uncertainty after JEM announced Khalil's death.

But the new leader inherits a movement that has been weakened by chronic war and divisions, said Magdi El Gizouli, a fellow at the Rift Valley Institute, a non-profit research and advocacy group.

"Gibril won't really change the situation much," he said. "Unless he has some regional backing, his options are limited."

In July, Khartoum signed the Doha Document for Peace in Darfur with the Liberation and Justice Movement, an alliance of rebel splinter factions.

But the JEM did not join, saying key issues, including power and wealth sharing, human rights violations, and the almost two million displaced by the conflict, had not been resolved.

Two factions of Darfur's Sudan Liberation Army, which together with JEM represent the main rebel groups in the region, also rejected the Doha deal.

In November the holdouts formed a "revolutionary front" to overthrow the Khartoum government, teaming up with the SPLM-N rebels based in South Kordofan and Blue Nile, contested regions bordering newly independent South Sudan.

The rebels say they are in a struggle for "democracy and civil rights" against an Arab-dominated regime unrepresentative of the country's political, ethnic and religious diversity.

Ibrahim Gambari, who heads the joint African Union-United Nations peacekeeping mission to Darfur, told AFP on Wednesday that JEM appeared to have split into factions since Khalil Ibrahim's death.

Until his successor was named, it remained unclear whether more groups can sign up to the peace deal inked in Qatar last year, Gambari said.

"We would have preferred a JEM that was intact, as a negotiating partner," he said.

"It looks like" JEM has factionalised, Gambari added, but much depended on the outcome of the group's leadership meeting.

"We'll have to wait and see what leadership emerges, how much support such a leadership has, and then we'll take it from there," said the Nigerian mission chief who is also interim chief mediator.