A bus and truck convoy was taking some 3,500 South Sudanese back to their ancestral homeland from Sudan on Monday, a church leader said, in the first major repatriation for months.

But the United Nations says around 40,000 other South Sudanese are still waiting for funding to help transport them from Sudan, where they live in "appalling" conditions at Khartoum-area squatter camps.

About 100 supporters of Egypt's deposed Islamist president Mohammed Morsi demonstrated in Sudan on Monday against the start of his trial in Cairo over the deaths of protesters.

The group, carrying pictures of the bearded Morsi, gathered across from Egypt's embassy in the Sudanese capital Khartoum, an Agence France Presse reporter said.

South Sudan's controversial opposition leader Lam Akol returned home for first time in two years Saturday, after a presidential pardon cleared him of allegations of encouraging armed rebels.

Akol was a former warlord who fought on both sides during Sudan's 1983-2005 civil war, and the biggest critic of South Sudan's President Salva Kiir since splitting from the ruling party in 2009.

Carjackers killed a Sudanese aid worker in the country's Darfur region, the U.N. said, bringing to four the number of humanitarian staff killed this year in the region's worsening unrest.

The attack happened on October 23 about 15 kilometers (nine miles) southwest of Nyala, Sudan's second largest city, the United Nations Office for the Coordination of Humanitarian Affairs (OCHA) said in its latest weekly bulletin, issued late on Thursday.

Sudanese Islamist scholars have formed a National Movement for Change that hopes to lead a search for alternatives to the country's "failed" political system, a member said Thursday.

"We are calling on other people from different political or cultural (groups) or think tanks to join us to try to find a new way for Sudan," Khalid Tigani, one of about 10 members of the group, told Agence France Presse.

Residents of the flashpoint Abyei region claimed by both Sudan and South Sudan voted on the third and final day Tuesday in an unofficial referendum to decide which country they belong to.

The vote, which is organised by only one of the two peoples who count Abyei as home, is not recognized by either Khartoum or Juba, and has been criticized by the African Union as a "threat to peace".

African Union chief Nkosazana Dlamini-Zuma warned Monday that a vote in the flashpoint Abyei region claimed by both Sudan and South Sudan was illegal and risked sparking a return to war.

Dlamini-Zuma said the "unilateral act is unacceptable and irresponsible" in a statement that "condemns this exercise in the strongest terms possible".

Residents of the flashpoint Abyei region claimed by both Sudan and South Sudan were voting on Monday in an unofficial referendum to decide which country they belong to, a move likely to inflame tensions in the war-ravaged region, officials said.

"The people are voting to choose to join South Sudan or to be part of Sudan," Rou Manyiel, chairman of the Abyei civil society organization, told Agence France Presse.

The African Union on Sunday accused the Sudan government of preventing an AU delegation from visiting Abyei following talks that failed to make progress on the flashpoint region.

The AU "expresses its deep disappointment and regret that it was unable to undertake the visit (Saturday and Sunday)", it said, accusing Khartoum of postponing it "for contrived security reasons".

Three leading reformers faced with expulsion from Sudan's ruling party are forming a new one following a deadly crackdown on protests last month, one of them said Saturday.

"We decided to establish a new party carrying the hopes of the Sudanese people," Fadlallah Ahmed Abdallah, an MP with the governing National Congress Party (NCP), told Agence France Presse.