Food shortages and fighting between government forces and rebels have forced almost 3,000 people to flee their homes in Sudan's Blue Nile state, the United Nations said on Wednesday.

The latest displacement comes after Defense Minister Abdelrahim Mohammed Hussein said in November that an operation had begun to crush Sudanese rebels.

Three Sudanese have been jailed for three to five years for arson and looting during fuel-price protests in September, police said Tuesday.

Theirs were among the first major sentences handed down for the worst urban unrest of President Omar al-Bashir's 24-year rule.

One rebel fighter was killed and three were wounded in Sudan's Blue Nile state during attacks against military convoys that also left several government troops dead, the insurgents said Tuesday.

Sudan's army spokesman could not be reached for comment.

Sudan's ruling party on Sunday named as senior vice president a man once dubbed a "sinister" defender of the Islamist revolution which brought President Omar al-Bashir to power.

Bakri Hassan Saleh, a former interior and defense minister, was named first vice-president as Hassabo Mohammed Abdel Rahman became second vice-president, senior party official Rabbie Abdelatti Ebaid told Agence France Presse.

Sudan's Vice-President Ali Osman Taha, a key figure behind the Islamist-backed coup 24 years ago, has resigned to pave the way for a new government, President Omar al-Bashir said Saturday.

"Ali Osman will voluntarily step down", as he did in 2005 following the signing of a peace agreement that ended 22 years of civil war, Bashir was quoted by the official SUNA news agency as saying.

Key leaders of South Sudan's ruling party charged President Salva Kiir with "dictatorial" behavior Friday, warning of instability threatening the young nation in a deeply controversial challenge to his rule.

The group were led by powerful politician Riek Machar, a charismatic but controversial leader who fought on both sides of Sudan's brutal 1983-2005 civil war, and who was sacked as vice-president in July.

Sudan and Ethiopia on Wednesday were to inaugurate a cross-border electricity link which an analyst said aims to strengthen Khartoum-Addis Ababa ties as tensions persist with Egypt over a giant dam.

Ethiopian Prime Minister Hailemariam Desalegn would attend the ceremony in Sudan's eastern city of Gedaref, the official SUNA news agency reported.

Rebels and government forces in Sudan's South Kordofan state have clashed again south of a railway town the insurgents briefly occupied last month, both sides said on Monday.

Fighting in the state has intensified since early November, at the start of the dry season, as the government began an operation to crush the ethnic rebels who rose up two years ago.

More than 11,000 Sudanese workers have returned voluntarily from Saudi Arabia after an amnesty for foreign employees to legalize their status, official media said on Saturday.

"The number of Sudanese that have voluntarily returned from Saudi Arabia has reached 11,678 as the amnesty for people working in the country without proper permits expired on November 4", the state SUNA news agency reported, quoting Khalid Fath al-Rahman, deputy head of Sudan's embassy in Riyadh.

Several people have been reported killed in an air strike in Sudan's volatile Darfur region, international peacekeepers said Saturday.

"UNAMID has received information from local sources that several people were killed by an alleged air strike while travelling from Tabit to Shangil Tobaya," a public information officer from the African Union-U.N. Mission in Darfur told Agence France Presse.