Deaths blamed on gang who invaded base where civilians were sheltering, while Obama calls for end to violence

Three United Nations peacekeepers from India were killed when a base sheltering civilians in South Sudan was stormed on Thursday, officials have said.

The compound of the UN mission in Akobo was besieged by local youths from the Nuer community intent on revenge for alleged targeted killings of their kinsmen in the capital, Juba.

Witnesses in Akobo, in South Sudan's restive Jonglei state, said the perimeter was overrun and civilians, government officials from the country's most populous tribe, the Dinka, and UN peacekeepers were among the casualties.

India's UN ambassador, Asoke Mukerji, said three of his country's troops were killed. It was the first announcement of UN fatalities from this week's upsurge of ethnic-based violence.

In Washington, Barack Obama issued a statement saying the conflict threatened to derail progress South Sudan has been making since gaining independence. "Inflammatory rhetoric and targeted violence must cease," the US president 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."

After the announcement by Mukerji at a meeting on UN peacekeeping, his Pakistani counterpart, Masood Khan, asked for a minute of silence and diplomats rose to pay tribute to the fallen soldiers. Mukerji said that "unfortunately, just this very morning such militia groups have targeted and killed three soldiers from India in South Sudan".

Foreign nationals still in South Sudan crowded the airport in the capital, Juba, trying to escape. Britain's Foreign Office (FCO) said that after an air evacuation of some UK nationals on Thursday, a second plane would arrive on Friday. "We strongly advise all British nationals in South Sudan to leave the country if they can do so safely. You may have difficulty leaving in the event of a further deterioration in security," the FCO warned in a statement.

"British nationals choosing to remain in South Sudan should remain alert to the local security situation, monitor the media and stay in a safe location."

The UN has called on Yoweri Museveni, president of neighbouring Uganda to urgently mediate, while emergency flights have been laid on to help evacuate aid workers, diplomats and expats.

A Nuer-led rebel militia, which claims its community is under attack by the government of South Sudan, has seized Bor, one of the country's most strategically important towns.

The militia made up of military mutineers from the Sudan People's Liberation Army (SPLA) has been raised under the command of the defected General, Peter Gadet, who believes his own tribe, the Nuer, are under attack. After the storming of the UN base, Gadet said he would intervene to prevent further killings.

"It's an important distinction that the Akobo attack was not carried out by the armed opposition but by local youths," said Casie Copeland, a South Sudan expert with the Brussels-based monitor the International Crisis Group.

As fighting in the world's newest nation has erupted in new areas beyond the capital, Juba, disturbing testimony has emerged pointing to civilian casualties and ethnically-targeted killings. Since Wednesday, the heaviest clashes have come in Bor, the main town in the notoriously restive Jonglei state which is criss-crossed by some of the young country's most aggravated ethnic fault-lines.

Map of South Sudan. Graphic: theguardian.com

Civilians had taken refuge with peacekeepers at the United Nations base in Bor where an unknown number of casualties were being treated.

"All the refugees are in this compound," said a witness before the attack, who was also inside but asked not to be named. "We're hearing shooting in the town, there is shooting everywhere."

He said that children were among the dead and wounded brought to the base. Peacekeepers had remained inside the UN compound while fighting raged outside.

"Outside they're burning houses and looting, no-one can leave the compound," he said.

Since clashes broke out in Juba on Sunday fighting has occurred in half of the country's ten states. Victims and witnesses told the New York-based monitor, Human Rights Watch, that government soldiers and police have been interrogating people on the street in Juba about their ethnicity and deliberately shooting ethnic Nuer.

"The awful accounts of killings in Juba may only be the tip of the iceberg," said HRW's Daniel Bekele.

Much of the fighting has pitted government forces loyal to the ethnic Dinka president, Salva Kiir, against soldiers and civilians from the Nuer community.

The first flights out of South Sudan's capital reached neighbouring Kenya on Wednesday night where terrified escapees described hit squads going house-to-house in Juba.

"People think it's getting better," said aid worker Mo Ali who had been in the country for four years. "But it's like a cancer, you think you're just about to get some part of it sorted out and something else springs up."

He said he had seen snipers just 50 feet from where he was staying: "You could smell the gunshots… and hear the shockwaves of what sounded like tank-fire or mortar-fire."

Doctors at Juba's teaching hospital said they were treating nearly 300 people for gunshot wounds, most of them young men, although not all in military uniform. Its facilities have been overrun, they said, and the tiny mortuary was filled with decomposing bodies. The Red Cross and other organisations donated 250 body bags but were told that more were needed.

Meanwhile, respected former government minister Jok Madut Jok said South Sudan was facing a possible slide into civil war if political leaders did not agree to urgent talks.

Having just returned from an academic post in the US, he said in an open letter that the violence had been triggered by infighting in the multi-ethnic presidential guard, also known as the Tigers. Guard members from South Sudan's two largest communities -- the Dinka and the second most populous, the Nuer -- had an argument that turned into a shooting match. When Nuer members of the Tigers climbed onto a roof adjacent to the president's residence and started to fire into it, they were hit in return with artillery fire. The attack on President Kiir's compound prompted accusations of an attempted coup. A roundup of prominent critics of the government, including at least eleven former cabinet members began and the president blamed prominent Nuer politician, Riek Machar, the man he sacked six months ago from the vice president's job.

After furious denunciations from Mr Kiir, reprisals have followed against the Nuer people in Juba. Soldiers dragged the Nuer pastor, Reverend Simon Nyang Lam, out of his house in the capital and killed him. "He thought he would be ok because he was a pastor," a relative told HRW.

Other witnesses described how seven Nuer men were killed in the compound where they were sheltering. Some of them died when soldiers shot into the building, others were gunned down as they climbed through a window and one man was shot dead as he hid in a water barrel.