The United Nations Security Council on Thursday urged Sudan and South Sudan to swiftly resume negotiations on the disputed oil-producing region of Abyei after talks earlier this week ended without an agreement.

Council members reiterated "their grave concern about the highly volatile situation in Abyei area" according to a statement read by the President of the Council, Azerbaijan's Agshin Mehdiyev.

Sudanese President Omar al-Bashir arrived in South Sudan Tuesday, as pressure mounts over the contested flashpoint enclave of Abyei and other bitter issues left unresolved since the countries split two years ago.

Bashir, an indicted war crimes suspect wanted by the International Criminal Court, was met at the airport in Juba by his southern counterpart Salva Kiir, with the former arch-enemies shaking hands and then embracing.

Large numbers of civilians have been killed and wounded in attacks in South Sudan's troubled Jonglei state, the United Nations Mission in South Sudan (UNMISS) said Monday.

Authorities in South Sudan have blamed fighters loyal to anti-government rebel leader David Yau Yau, and said 78 people were killed in Sunday's attacks on villages in Twic East county.

The United States on Tuesday called on Sudan to investigate the killings of three UN peacekeepers in an ambush in the troubled western Darfur region.

Three Senegalese troops died, and a fourth was wounded, when a water convoy they were escorting was attacked on Sunday on a road from the town of El Geneina to the UN mission in Darfur (UNAMID) headquarters in West Darfur.

Sudan's President Omar al-Bashir has arrived in Saudi Arabia to perform the hajj with other Muslim pilgrims, official media said Sunday, after dozens died in his country during recent protests.

Bashir "arrives in Jeddah to perform hajj," the state SUNA news agency reported.

A Zambian military observer was killed by unidentified assailants in Sudan's North Darfur state, U.N. officials said Saturday.

The attack, which killed the member of the African Union-United Nations Hybrid Operation in Darfur (UNAMID), occurred Friday in the city of El Fasher.

The U.N. Security Council is expressing alarm at the imminent threat of the spread of polio through Sudan's violence-wracked South Kordofan and Blue Nile states and the continuing outbreak of polio in the Horn of Africa.

The U.N. humanitarian office has reported that the threat affects more than 165,000 children in the two Sudanese states "due to a lack of immunization in the border area in more than two years," the Security Council said in a statement Friday.

Sudan's President Omar al-Bashir on Wednesday said deadly protests over fuel-price increases last month were part of an effort to topple his regime.

"After we announced the latest economic measures they said this is a chance to overthrow Ingaz," he said in a reference to his government which took power in a 1989 Islamist-backed coup.

A Sudanese judge on Sunday threw out charges against 19 people who were among hundreds rounded up after deadly protests sparked by fuel price hikes, a lawyer said.

The judge said he found "no evidence against them", one of their lawyers, Mutasim al-Haj, told Agence France Presse.

Hundreds of men and women marched for "freedom" in the Sudanese capital on Friday despite the deployment of militia, troops and riot police, Agence France Presse reported.

One of the largest rallies occurred in the poor Shambat area of North Khartoum, where several hundred residents marched along the dirt roads between their houses.