Amnesty International said Wednesday that Sudanese security officers were reportedly involved in attacks over gold mining that killed up to 200 people, in one of the Darfur region's worst recent outbreaks of violence.

The unrest displaced more than 70,000 people, the U.N. has said, citing government figures.

At least five people were killed in South Sudan's troubled Jonglei state in clashes between government troops and rebel soldiers who had come for peace talks, officials said Monday.

Hundreds of civilians fled the clashes which broke out Sunday -- during which the market in the remote town of Pibor was set on fire -- as a government delegation arrived to negotiate with the breakaway commander of a local rebel movement.

Kidnappers freed 11 Sudanese engineers and road builders in Sudan's troubled Darfur region on Saturday, after the earlier release of their four Chinese co-workers, official media said.

News agency SUNA said they were all abducted by gunmen on January 12 as they finished their work in al-Kuma district, northeast of El Fasher, the capital of North Darfur state, which has seen a resurgence of violence in recent months.

Rival leaders of Sudan and South Sudan are expected to meet Friday in the Ethiopian capital in the latest attempt to implement stalled oil, security and border deals, officials said Wednesday.

Sudanese President Omar al-Bashir and his Southern counterpart Salva Kiir will meet face-to-face at African Union mediated talks for the second time this month to push deals settled after bloody border conflict broke out last year.

A former top U.N. official in Sudan on Friday warned that "ethnic cleansing" is going on in the southern part of Sudan, where the people are suffering from hunger, disease and bombing in two war-torn states.

Just back from a trip to Blue Nile and South Kordofan states, where conflict between rebels and Sudanese government forces has raged for over a year, Mukesh Kapila called on the international community to come to the aid of the some 1.5 million people living in these states that border South Sudan.

South Sudan said Thursday it had started withdrawing troops from its contested border with Sudan, as part of an agreement to demilitarize the flashpoint area that sparked a major conflict last year.

After months of talks, the two former civil war foes agreed to set up a "Safe Demilitarized Border Zone" (SDBZ) along the largely undefined border as part of a raft of deals signed in September during African Union-brokered negotiations that had so far failed to bear fruit.

Four Chinese workers abducted by Darfur rebels on January 12 have been freed, a spokeswoman for the joint U.N.-African Union peace keeping force in the troubled western Sudan region said Wednesday.

"The four abducted Chinese workers were released and delivered to the headquarters of the UNAMID mission in the South Darfur region of Khour Abchi," spokeswoman Aicha Elbasri told Agence France Presse.

Armed men have kidnapped four Chinese nationals and five Sudanese workers engaged in road construction in Sudan's strife-ridden Darfur region, the official SUNA news agency reported on Monday.

The attackers abducted the men and seized their vehicles on Saturday as they were finishing their work for the day, the report said, without naming the construction company nor indicating who was behind the kidnapping.

Sudan's army claims to have killed more than 50 rebels in clashes in South Kordofan state, the official Sudanese news agency SUNA reported late Friday.

Government troops had pushed back an attack by rebels in the region, killing more than 50 and suffering some dead and wounded themselves, SUNA reported, citing an army statement.

Hundreds of thousands of people in Sudan's conflict-stricken South Kordofan are surviving on roots and leaves, a top U.N. official told the U.N. Security Council on Tuesday.

About 700,000 people in South Kordofan and neighboring Blue Nile states face "truly appalling" conditions while the Sudan government and rebels block access to international aid workers, U.N. humanitarian operations director John Ging said.