The United Nations says that Sudan has launched a massive vaccination campaign to immunize 2.4 million people against an outbreak of yellow fever in the restive region of Darfur.

The Monday statement from the U.N. Office for the Coordination of Humanitarian Affairs says Khartoum's Health Ministry received an initial shipment of 800,000 doses of vaccine on Friday.

The U.N. Security Council on Friday called on Sudan and South Sudan to step up efforts to end their wrangling over a disputed territory wracked by protests this week.

A council resolution renewing the mandate of a U.N. peacekeeping force in Abyei demanded that the rival neighbors "urgently" agree nominations for a government for the territory and set up a police force.

Political talk flowed as freely as booze in the lively Khartoum of decades past, and The Grand Hotel was its fountain.

Behind the colonial-era walls, deals were made and gossip exchanged by an elite group of civil servants, politicians, intellectuals and businessmen.

A local staff member with the U.N.'s peacekeeping force in the Abyei region contested by Sudan and South Sudan has been killed in an incident that followed a tribal dispute, a U.N. official told Agence France Presse on Wednesday.

The employee, a member of the Dinka tribe, "was shot and killed" on Tuesday, Damian Rance, a public information officer with the U.N.'s humanitarian agency in Khartoum, told AFP.

More than 3.5 million people in Sudan's conflict-plagued Darfur region will be vaccinated against yellow fever which is suspected of killing nearly 100 people in the past seven weeks, officials said.

"(The) vaccination plan has been finalized and will cover vaccination of approximately 3.6 million," said a joint report from the U.N.'s World Health Organization and Sudan's health ministry, issued late Monday.

International peacekeepers on Monday expressed grave concern about an upsurge of violence in Sudan's Darfur, after they airlifted people wounded in recent clashes.

The fighting on Friday between government forces and "an armed group" near Shangil Tobay "is part of a larger pattern of conflict in the area in recent months," said the African Union-United Nations Mission in Darfur (UNAMID).

Sudanese rebels on Saturday said they captured one government armored vehicle and destroyed others in a battle near the capital of North Darfur state, which has seen an upsurge in violence.

The Justice and Equality Movement (JEM) said insurgents on Friday afternoon attacked a large government convoy traveling north from Shangil Tobay, which is about 50 kilometers south of El Fasher, the state capital.

Rebels in Sudan's war-torn South Kordofan state claimed on Thursday to have shot down an air force Antonov bomber, which they said crashed in flames along the undemarcated border near South Sudan.

Neither Sudan's military spokesman nor independent witnesses in the remote area, where access for journalists is restricted, could be reached for comment.

Sudan's President Omar al-Bashir has been discharged from hospital in Saudi Arabia and is recovering, his press secretary said on Wednesday, after a second minor operation in less than four months.

"President Bashir left the hospital today at 8:00 am local time," and is now recovering in the Saudi kingdom before continuing with his schedule there, Emad Sayed Ahmed told Agence France Presse.

Sudan's veteran Islamist leader Hassan al-Turabi, linked to al-Qaida leader Osama bin Laden in the 1990s, hopes U.S. President Barack Obama will win a second term on Tuesday.

"Obama of course," Turabi told Agence France Presse when asked about his U.S. presidential preference during an interview.