A large retaliatory attack by armed nomadic tribesmen on the rebel Sudan Liberation Movement/Army (SLM/A) on Monday left more than 40 people dead in the strife-torn western Sudanese region of Darfur, local sources said.

The attack was reportedly a response to a raid by the SLM/A on the village of Malam on 25 August, some 50 km from the South Darfur capital, Nyala, during which the rebels abducted children belonging to the Arab nomads living in the area.

According to the African Union Mission in Sudan (AMIS), the rebels also stole more than 2,000 camels and killed three civilians and three government solders.

The SLM/A rebels claimed that they seized the camels after the animals invaded their farmland and the nomads refused to move them out.

"Following a week-long truce, the AU [African Union] was unable to convince the SLA to return the camels. A few evenings after the truce ended, a large group of nomads attacked an SLA stronghold in the Jebel Marra mountain area [in South Darfur state]," a source within the nomadic community said.

The fighting lasted four or five hours, he added, and 30 nomads were killed.

During the skirmish, approximately 10 to 15 rebels also were killed, according to a humanitarian source who was in the Jebel Marra when the attack occurred.

"There are so many casualties - at least 30 - in Nyala military hospital, some of them severely wounded," she observed. "The situation is very tense and the nomadic tribesmen are calling for revenge."

Another local source confirmed that "a big mobilisation of Arab tribesmen" was underway and warned about the "intensification of combat operations" in the region.

Banditry and continuous attacks by armed groups on humanitarian workers, Arab nomads and villages in Darfur have increased significantly over the past weeks and threaten to destabilise the fragile ceasefire in the volatile western Sudanese region.

Observers on the ground have warned repeatedly that Darfur was at risk of descending into a perpetual state of lawlessness, even as the Sudanese government and the main rebel groups in the war-torn region discussed the possibility of a peaceful resolution to the conflict.

The sixth round of the Abuja peace talks between the government and the two main rebel groups - the SLM/A and the Justice and Equality Movement (JEM) - resumed in the Nigerian capital on Thursday amid mutual recriminations. Little progress has been made so far.

The nomadic source noted that the nomad leaders were worried that any Abuja treaty would fail to address the grievances of these communities.

"They don't think their interests are being represented," he observed. He admitted, however, that because the toll of the Darfur conflict had become prohibitively high in nomadic communities and they were "ready to surrender."

Nomadic groups were looking for a venue to negotiate with the farming communities, he added.

A proposed solution would include the creation of permanent villages for the large number of nomads who want to give up their itinerant lifestyle as well as an agreement between nomads and farmers on safe, fixed post-harvest routes for nomads to follow while migrating through Darfur.

The conflict in Darfur pits Sudanese government troops and allied militias like the Janjawid - accused of terrorising the region's non-Arab tribes - against two main rebel groups, the SLM/A and the JEM, who claim to be fighting against the marginalisation of their region by Khartoum.