Less than three years after its creation, the world's newest country is beginning to fracture along ethnic lines in violence that has killed hundreds of people, including three United Nations peacekeepers. What could come next, some warn, is ethnic cleansing.

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 — this week, even among the presidential guard.

On Thursday, armed youths breached a UN compound in Jonglei state, causing an unknown number of casualties.

"Unfortunately, just this very morning such militia groups have targeted and killed three soldiers from India in South Sudan," India's U.N. Ambassador Asoke Mukerji told a U.N. meeting on peacekeeping Thursday evening.

Evacuation flights

It was the first announcement of UN personnel 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 fallen soldiers.

In the capital, Juba, emergency evacuation flights took away American and British citizens, aid workers and United Nations personnel to escape the violence.

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," a statement from his office said late Thursday.

South Sudan's government declared that its security forces "are in absolute control of the situation," but admitted later Thursday 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.

South Sudan Violence

A United Nation soldier stands guard as civilians arrive at a UN compound adjacent to Juba International Airport to take refuge. (Rolla Hinedi/UNMISS/Associated Press)

"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, who spoke in Nairobi, Kenya.

Violence broke out late 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 Laam. Violence in Juba spiraled 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 earlier said an attempted coup had triggered the violence, and the blame was placed on ousted Vice President Riek Machar, an ethnic Nuer.

Machar disputed Kiir's allegations that he had attempted a coup, but said he wants Kiir out of power.

"We want him to leave. We want him to leave. That's it," Machar told Radio France Internationale. "He can't unite the people and he kills them like flies."

Machar, an influential politician who is a hero of the brutal war of independence against Sudan, is Kiir's rival for top leadership of the Sudan People's Liberation Movement party. Tensions had been mounting since Kiir fired Machar as his deputy in July. Machar later said he would contest the presidency in 2015.

Regardless of the cause, the South Sudan government said the violence has already killed up to 500 people.

Armed ethnic Nuer youths breached a UN compound in the tiny Jonglei village of Akobo, near the Ethiopian border, to reach civilians believed to be Dinkas seeking shelter there, said UN spokesman Farhan Haq in New York. "We fear there may have been some fatalities but can't confirm who and how many at this stage," Haq said.

At the time, 43 Indian peacekeepers, six UN police advisers and two UN civilian employees were present at the base, as were about 30 South Sudanese who had sought shelter, according to the UN mission in South Sudan. The mission said it would dispatch aircraft early Friday to evacuate UN personnel who remain at the base.

South Sudan's capital was mostly peaceful Thursday, and the government tried to assure the UN and foreign embassies "that civil tranquility has been fully restored."

Countries such as the U.S., Britain, Italy and Germany continued to evacuate residents. A plane with a mechanical malfunction blocked the runway during the day, jamming up inbound and outbound flights.

The U.S. evacuation plane — the fourth group of Americans flown out in two days — was eventually able to take off heading for Kenya. "Runway clear. Wheels up," the embassy said on Twitter. Two military flights and a charter took off on Wednesday. Britain's evacuation plane landed in Uganda late Thursday.

The government said it lost control of Bor, the capital of Jonglei state, to forces loyal to Machar. Gunfire was reported early and late in the day, and the UN used four helicopters to transport 75 people — a mix of aid workers and UN staff — to Juba, said Challiss McDonough, a spokeswoman for the UN's World Food Program.