US president Barack Obama has urged clashing factions in South Sudan to end violence, restore calm, and work toward reconciliation.
Mr Obama said the conflict in the country threatened to derail progress it has made since gaining independence in 2011.
“Inflammatory rhetoric and targeted violence must cease,” he said. “All sides must listen to the wise counsel of their neighbors, commit to dialogue and take immediate steps to urge calm and support reconciliation.”
Three United Nations peacekeepers are among the latest victims of the violence in South Sudan, which has killed hundreds.
The world's newest country is beginning to fracture and some are warning that ethnic cleansing could follow. South Sudan's numerous ethnic groups have battled each other for decades, but for years their animosity was united in hatred of the government in Khartoum, Sudan, the country's former capital.
When the south gained independence in 2011, the groups’ common enemy receded, exposing the fault lines - even among the presidential guard this week.
In the latest outrage armed youths breached a UN compound in Jonglei state yesterday, causing an unknown number of casualties, including the three Indian peacekeepers.
"Unfortunately, just this very morning such militia groups have targeted and killed three soldiers from India in South Sudan," India's UN ambassador Asoke Mukerji told a meeting of the world body.
It was the first announcement of UN staff killed in this week's upsurge of violence. Pakistan's UN ambassador Masood Khan asked for a minute of silence and diplomats rose to pay tribute to the soldiers.
In the capital Juba, emergency evacuation flights took away American and British citizens, aid workers and UN staff to escape the violence and UN secretary general Ban Ki-moon again urged political dialogue.
“The future of this young nation requires its current leadership to do everything possible to prevent South Sudan descending into the chaos that would be such a betrayal of the ideals behind its long struggle for independence,” his office said.
South Sudan’s government declared that its security forces “are in absolute control of the situation” but admitted later that the central government had lost control of Bor, the capital of the country’s largest and most populous state, where barrages of gunfire were reported.
“The situation in South Sudan can be best described as tense and fragile. If it is not contained, it could lead to ethnic cleansing,” said Choul Laam, a top official with the ruling Sudan People’s Liberation Movement.
Violence broke out late on Sunday when the presidential guard splintered along ethnic lines. Guards from the president's majority Dinka tribe tried to disarm guards from the Nuer ethnic group, said Mr Laam. Violence in Juba spiralled from there, and then extended out into the country.
"The awful accounts of killings in Juba may only be the tip of the iceberg," said Daniel Bekele of Human Rights Watch. "Government officials — whatever their politics — need to take urgent steps to prevent further abuses against civilians and quickly deescalate rising ethnic tensions."
President Salva Kiir said earlier an attempted coup had triggered the violence and blamed ousted vice president Riek Machar, an ethnic Nuer.
Mr Machar disputed Mr Kiir’s allegations that he had attempted a coup, but said he wanted him out of power.
“We want him to leave. We want him to leave. That’s it,” Mr Machar told Radio France Internationale. “He can’t unite the people and he kills them like flies.”
Mr Obama has sent 45 military staff to South Sudan to protect American citizens and property.
AP