Former Darfur rebels accused Khartoum on Thursday of arming and training forces of a tribal militia who have killed 170 civilians in South Darfur in recent days, but the Sudanese army rejected the charge.

The Darfur conflict began 4-1/2 years ago in the north of the arid region, but the spread of weapons to other tribes in the south over the past 18 months has increased tensions in these previously safer areas.

The Sudan Liberation Movement (SLM) of Minni Arcua Minnawi, the only rebel faction to sign a peace deal last year, said its forces had intervened to stop attacks by the Arab Maaliya tribe and discovered the militia had support from Khartoum.

"We engaged them in battle but it was clear that they had capabilities beyond those of militia," said the faction's military spokesman Mohamed Hamid Dirbeen, who had just returned from the area, adding that the SLA had lost eight men.

Dirbeen said the Maaliya fighters wore new military uniforms and had heavy artillery and weapons provided by Khartoum.

"There is air support, planes and helicopters from the Sudanese army landing in the militia areas," he said. "They have armed and supported them," he added. He said the militia had killed 170 civilians and also stolen cattle.

A Sudanese army spokesman said the accusations were untrue.

"How can we arm militias to fight against civilians? This is not true," he said.

SHAKY CEASEFIRE

International experts estimate 200,000 have died and 2.5 million have been driven from their homes after mostly non-Arab rebels took up arms in early 2003 accusing Khartoum of marginalising the remote region.

Khartoum mobilised militia to quell the revolt and the International Criminal Court (ICC) has issued arrest warrants for a junior government minister and militia leader accused of conspiring in war crimes.

Dirbeen said Minnawi would continue to abide by the peace deal, but said the African Union, monitoring the shaky Darfur ceasefire, was not capable of investigating the events and urged U.N. or European Union intervention.

Since the ceasefire, the Darfur insurgents have split into more than a dozen factions. Last month, the U.N. Security Council authorised a 26,000-strong U.N.-African Union peacekeeping force for the region.

Adila town, near to the clashes involving the Maaliya tribe, witnessed heavy fighting last week between another rebel faction, the Justice and Equality Movement (JEM) and the government last week.

The United Nations said it had reports the hospital in Adila had been looted and was sending medical supplies.

"A large number of the population in Adila town had left as a result of the fear of insecurity," said Maurizio Giuliano, spokesman for the U.N. office for the coordination of humanitarian affairs (OCHA).

"Despite this we know the majority have now returned."

The world's largest aid operation helps some 4.2 million in need in Darfur. But some 500,000 are out of reach because of insecurity and banditry.