Musa Hilal, who is accused of leading militias on a state-sponsored campaign to cleanse parts of Darfur of non-Arab farmers, will act as special advisor to the minister of federal government, local media reported.

The appointment was made despite Hilal facing a United Nations travel ban and sanctions for his role in the conflict, and ahead of his possible indictment by the International Criminal Court for alleged war crimes.

Hilal has admitted recruiting local Janjaweed militias for the government, but denies personal involvement in the scorched earth campaign that has driven more than two million people from their homes, and seen more than 200,000 people die.

He told Reuters on Sunday that his new role would be based in Khartoum but would include travel to outlying areas.

Analysts say Hilal's nomination will act as a further stumbling block to efforts to persuade Darfur's myriad rebel groups to enter peace talks with the government, who they accuse of condoning and even rewarding those people responsible for the worst atrocities in Sudan's western region.

In September, President Omar al-Bashir appointed Ahmad Muhammad Harun, one of two men sought by the International Criminal Court for war crimes in Darfur, as state minister for humanitarian affairs. The other accused, an alleged Janjaweed leader known as Ali Kushayb, was freed from jail the following month.

Richard Dicker, director of the International Justice Program at Human Rights Watch, said the UN secretary general, Ban Ki Moon, who is due to meet President al-Bashir during an African Union summit next week, should insist that Hilal's position is revoked.

"Musa Hilal is the poster child for Janjaweed atrocities in Darfur," said Dicker. "Rewarding him with a special government post is a slap in the face to Darfur victims and to the UN Security Council."

In April 2003, shortly after a rebel attack on a Darfur army base that triggered the conflict, Hilal, the son of a famous paramount chief, was released from prison in Port Sudan where he was serving a sentence for robbery. He immediately returned to Darfur, convening a meeting where he reportedly ordered Arab tribesman to attack all non-Arab villages and steal their livestock. He was given arms and supplies by the government.

In a Guardian interview in 2004, Hilal said that he raised a militia from his clan to fight the rebellion launched by mainly African ethnic groups in Darfur.

"The government was putting forward a programme of arming for all the people," he said. "I called our sons and told them to become armed."

But rights groups allege that Hilal's role went far beyond recruitment. It says that he ran training camps for his fighters, and was present at the scene of several large attacks on villages in North Darfur.

As part of its case against Harun, prosecutors at the International Criminal Court described Hilal as a "notorious militia/Janjaweed leader" who spoke alongside Harun at a militia rally in 2003, making a "very racist" speech in which he talked of "holy war". The court said it will issue more indictments, and Hilal is thought to be high on the list of candidates.

Sally Chin, a Sudan analyst at the International Crisis Group, said Hilal's appointment came at a time when some Arab communities in Darfur were voicing anger at the government, and even forming alliances with rebel groups.

"Giving Hilal an official position is a disturbing move," she said. "It sends a very negative message to Darfur and to the negotiation process."