* The main rebel groups have refused to join the peace process
* Recent fighting has displaced more than 130,000 people
* Donor conference scheduled to be held in Doha next month
Sudanese rebels said on Saturday they had killed more than 200 soldiers in South Darfur, but the government said its troops had suffered only a "number" of casualties and repulsed an ambush.
War broke out in the western region of Darfur over a decade ago and has raged ever since despite two peace accords and the presence of the world's largest peacekeeping mission.
The main insurgent groups, who accuse the government of marginalising the region's ethnic minorities, have refused to join a Qatar-backed peace process that led to a deal between Khartoum and an umbrella of smaller rebel factions in 2011.
While violence is down from its peak in 2003 and 2004, new fighting has forced more than 130,000 people to flee their homes since the start of the year, according to the United Nations.
On Saturday, rebels of the Sudan Liberation Army faction loyal to veteran fighter Minni Minnawi said they attacked a government convoy near Nyala, the capital of South Darfur state.
"Nothing of note survived of the convoy," they said in a statement. They said they killed 260 government troops and militia fighters - an unusually high number to claim.
The army contradicted this account, saying it had repulsed the ambush and had killed and wounded around 100 rebels. The armed forces only suffered "a number" of casualties, the army's spokesman said in a report by state news agency SUNA.
Both sides frequently give conflicting reports of fighting, each claiming victory over the other. Events in Darfur are hard to independently verify because of restrictions on media access to the region.
Donors are scheduled to meet in Doha next month at a conference to raise money for development projects and other provisions of the 2011 peace deal.
In December, the outgoing U.S. special adviser for Darfur said Sudan had implemented little of the deal, which was hindered by a lack of funding, the failure to disarm militias and attacks on peacekeepers.
Sudan's President Omar Hassan al-Bashir is wanted by the International Criminal Court on charges of genocide and war crimes in Darfur. Khartoum dismisses the court as an agent of Western neo-imperialism.
In 2008, the United Nations said some 300,000 people may have died in Darfur's war, a figure some activists say is too low. The government has put the death toll around 10,000.