169 killed in South Sudan massacre

South Sudan, the world's youngest country, has been beset by civil war, poverty and massive corruption since it was formed in 2011.

The United Nations warns of a return to "all-out civil war" as a power-sharing deal between President Salva Kiir and his long-time rival, Riek Machar, has unravelled over the past year.

The desperately poor east African country also faces chronic ethnic violence and violent cattle-raiding.

The latest massacre happened early on Sunday in Abiemnom County near the Sudan border.

"A total of 169 bodies have been laid to rest in a mass grave," Elizabeth Achol, health minister in northern Ruweng administrative area, told AFP by phone.

Local information minister James Monyluak gave the same toll, saying it included women, children and elderly people and could increase further as more bodies are found.

A diplomatic source, speaking to AFP anonymously, placed the death toll at 70 but said it could rise.

Initial reports indicated the attack was carried out by an ethnic Nuer group, potentially in revenge for the killing of some traders, the diplomatic source added, though no group has claimed responsibility.

- Humanitarian workers hit -

Many residents have fled to nearby villages, while others have sought protection at a local UN compound, Monyluak said.

"The security situation has since stabilised, with government security forces deployed and now in control of the area," he added.

UN peacekeepers were "temporarily sheltering some 1,000 civilians within our base in the area and providing emergency medical care to the injured," a spokesperson for the UN Mission in South Sudan said.

Clashes between government and opposition forces have focused on Jonglei state in the last two months, where some 280,000 have been displaced according to the UN.

Humanitarian workers have also been targeted.

On Monday, Doctors Without Borders (MSF) said 26 members of staff were missing following an airstrike on one of its facilities.

The organisation has suspended medical services in Lankien and Pieri in Jonglei state.

UN rights chief Volker Turk voiced alarm Friday at the country's deteriorating situation, calling for swift action to avert a return to full-scale civil war.