Tribal clashes have reignited in Sudan's Darfur region, leaving up to 20 dead, local sources said on Monday.

A patrol from the African Union-United Nations peacekeeping mission reached Umm Dukhun and other areas of Central Darfur state to verify reports of fighting between the rival Misseriya and Salamat tribes, a UNAMID public information officer told Agence France Presse.

A Sudanese Christian who gave birth in prison after being sentenced to hang for apostasy was freed Monday but immediately went into hiding, fearing for her life, a lawyer said.

Official media confirmed that an appeal court annulled the earlier verdict against Meriam Yahia Ibrahim Ishag, 26.

Doctors Without Borders (MSF) is working in Sudan's war-torn South Kordofan despite Khartoum's denial of access to parts of the state, it said Monday, confirming some aid has got through.

Sudan tightly restricted the movement of aid agencies in South Kordofan after fighting with rebels of the Sudan People's Liberation Movement-North (SPLM-N) erupted in June 2011.

Two Sudanese employees of the Irish aid group GOAL have been abducted in the troubled Darfur region, the group said in a statement on Friday.

It is the latest incident of its kind in a region where crime and other violence has surged.

The number of civilians seeking refuge on U.N. bases from bloodshed in South Sudan has reached a peak of 95,000 since fighting broke out in December, the United Nations said Thursday.

There are more than 30,000 people on U.N. bases in the capital Juba, 18,000 in Malakal in Upper Nile State and around 38,000 in the oil hub of Bentiu, said spokesman Stephane Dujarric.

Sudan on Thursday appealed for Egypt to resume full participation in a 10-nation Nile River forum, four years after Cairo withdrew over fears for its access to the crucial water source.

Egypt has limited its participation in the Nile Basin Initiative since 2010 when Rwanda, Ethiopia, Uganda and Tanzania signed a new treaty on equitable sharing of Nile waters.

The ICC's chief prosecutor asked the United Nations Tuesday to investigate allegations that its Darfur mission had been covering up crimes by Sudanese forces against civilians and peacekeepers.

Fatou Bensouda, who presented the U.N. Security Council with her latest report on the situation in the Sudanese region, spoke of allegations that the U.N.-African Union Mission in Darfur (UNAMID) had "been subject to manipulation."

Sudanese jailers removed the chains from a Christian woman, sentenced to death for apostasy, after she gave birth in prison last month, one of her lawyers said Tuesday.

The case of Meriam Yahia Ibrahim Ishag sparked an outcry from Western governments and rights groups after a judge sentenced her on May 15 to hang.

Sudanese air force bombs have hit a Doctors Without Borders hospital in South Kordofan, the group said Tuesday, adding to Western concerns about attacks against civilians in a largely-hidden war.

Paris-based Medecins Sans Frontieres said its facility in Farandalla, South Kordofan, was "attacked".

Sudan's former prime minister Sadiq al-Mahdi was released from custody on Sunday, one month after state security agents detained him in a case that sparked concern from Western governments.

An Agence France Presse reporter saw a smiling Mahdi, chief of the opposition Umma party, greeting about 200 noisy supporters at his headquarters in Khartoum's twin city of Omdurman.