Juba: World leaders have stepped up efforts to pull South Sudan back from the brink of all-out civil war, as fighting rages across the country including in a key oil-producing region.
Special envoys from the US and Nigeria were flying into the capital Juba, following on from a mission by foreign ministers from east Africa and the Horn and after an appeal for an end to the violence from United Nations chief Ban Ki-moon.
Fighting has gripped South Sudan for a week, after President Salva Kiir accused his former deputy, Riek Machar, of attempting a coup. Mr Machar has denied this, and has accused Mr Kiir of carrying out a vicious purge of his rivals.
South Sudan's President Salva Kiir (right) receives Nigeria's acting Foreign Minister Nurudeen Mohammed at his office in Juba. Photo: AFP
The clashes have left hundreds dead and sent tens of thousands of people fleeing for protection in UN bases or to safer areas of the country.
The fighting has both ethnic and political dimensions, as troops loyal to Mr Kiir, an ethnic Dinka, battle forces backing Mr Machar, a Nuer, and the International Committee of the Red Cross (ICRC) said it was "alarmed" by reports of violence against civilians.
"We are extremely concerned about reports of both targeted killings of civilians and ill-treatment," said Melker Mabeck, head of ICRC's delegation in Juba. "Civilians must be protected from attack. Respect must be shown for human life and for the dignity of all people."
Foreign governments, including those of the US, Britain, Uganda, Kenya and Lebanon, have been organising special evacuation flights to pull out their nationals.
The US successfully evacuated its citizens overnight after an earlier attempt was aborted when the US planes came under fire by rebels.
"This morning, the United States - in coordination with the United Nations and in consultation with the South Sudanese government-- safely evacuated American citizens from Bor, South Sudan," the US State Department said. "US citizens and citizens from our partner nations were flown from Bor to Juba on UN and US civilian helicopters," the statement said.
Canberra has urged Australians in South Sudan to leave while they still can.
Foreign Minister Julie Bishop said the situation was "exceptionally volatile", and recommended any Australians who had not yet left to do so as soon as possible.
The UN began evacuating "non-critical staff" from Juba to Uganda and will send military reinforcements to embattled towns further north, it said on Sunday.
President Barack Obama warned against continued fighting, and has sent special envoy Donald Booth to Juba.
"Any effort to seize power through the use of military force will result in the end of longstanding support from the United States and the international community," the White House said.
South Sudan's government has acknowledged that much of Unity State, the country's main oil-producing area, was in the hands of the rebels.
Forces loyal to Mr Machar were also still in control of Bor, the capital of Jonglei state and situated about 200 kilometres north of Juba, although South Sudan's army spokesman said government troops were advancing to retake the town.
"The SPLA is still moving towards Bor, but have not yet captured Bor," Sudan People's Liberation Army spokesman Philip Aguer told AFP.
Mr Aguer confirmed that "Unity State is currently divided, with the SPLA and the loyalists to the government on one side and those who are supporting Riek Machar on the other.
"We are not in control of Bentiu and we don't know how many people are wounded and how many people are killed," Mr Aguer said.