United Nations secretary-general Ban Ki-moon is leading international calls for a renewed peace efforts in South Sudan, amid rapidly escalating political and ethnic violence.

South Sudan's president Salva Kiir, a member of the dominant Dinka ethnic group, has accused his former vice president Riek Machar, who is from a different tribal group and who was sacked mid-year, of attempting to seize power by force - something the former vice president denies.

Hundreds of people have been killed since violence erupted after a meeting last week of the National Liberation Council of the Sudanese People's Liberation Movement (SPLM) failed to lessen tensions in the ruling party.

Clashes erupted in Juba, the capital of the oil-rich state, and have since spread to more than a dozen separate parts of the country.

The escalating violence has sent tens of thousands in search of UN protection.

The UN estimates 35,000 civilians in six of the country's 10 states are sheltering at UN bases.

The UN Security Council has held an emergency meeting and expressed alarm and concern over the rapidly deteriorating security and humanitarian crisis.

Mr Ban urged SPLM leaders "to demonstrate compromise and leadership on behalf of the Southern Sudanese people, and to resolve their personal differences through dialogue immediately".

"The secretary-general reiterates his call for all parties to exercise restraint, and to cease hostilities," the UN leader said, one day after a deadly attack on one of its bases.

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In a sign of the nervousness amongst South Sudan's neighbours, a delegation of East African foreign ministers is in the country in an effort to broker peace.

The international diplomats said Mr Kiir agreed to take part in an "unconditional dialogue" on ending deadly strife in the country, UN Security Council president Gerard Araud said.

Mr Araud, France's UN ambassador, made the comments to reporters after an emergency UN Security Council meeting on the South Sudan crisis.

He initially said the former vice president had also agreed to dialogue, but he later corrected his comments.

"The members of the Security Council stressed the necessity for all parties to reject this violence in all its forms", he said, "and to resolve disagreements peacefully".

Ministers from Ethiopia, Kenya, Uganda, Djibouti and Sudan went to Juba on the mission to try to end a week of strife.

They held talks with Mr Kiir but not with Mr Machar.

The ministers were also to try to see detainees held since the fighting erupted on Sunday.

The 15-member Security Council urged the leaders to bring "a swift and peaceful resolution to this crisis by calling for a cessation of hostilities and immediately commencing a dialogue."

The council expressed "grave alarm" at the worsening crisis which it said was a threat to the whole region.

In a statement the US president, Barack Obama, has warned the country stands on the edge of "a precipice".

America has sent 45 troops but only to defend the American embassy, not to get involved in the conflict.

ABC/AFP