Five Indian peacekeepers and at least seven UN civilian workers were killed Tuesday in an ambush in South Sudan, officials said, in what the UN secretary general says could be a war crime.
Two hundred attackers took part in the raid on a UN convoy at Gumuruk in the country's troubled Jonglei state, UN peacekeeping spokeswoman Josephine Guerrero told AFP.
"We are still verifying their identities. But the peacekeepers were vastly outnumbered. It was a deliberate and targeted attack," Guerrero added.
The civilians included two workers for the UN mission in South Sudan (UNMISS) and five civilian contractors, according to an official UN toll.
UN Secretary General Ban Ki-moon and the UN Security Council condemned the attack in separate statements and called on South Sudan's government to "swiftly" bring the perpetrators to justice.
Ban "recalls that the killing of peacekeepers is a war crime that falls under the jurisdiction of the International Criminal Court," said his spokesman Martin Nesirky.
Nine people were injured and Ban said some are in "critical" condition. The United Nations originally said some staff remained unaccounted for, but all were later found.
Indian foreign ministry spokesman Syed Akbaruddin blamed unknown "rebels" who he said attacked while the soldiers were escorting a UN convoy.
The volatile eastern state of Jonglei has been the scene of widespread ethnic conflict since South Sudan became independent in July 2011, with bloody battles between rival tribes, including the Dinka, Lou Nuer and Murle people.
Clashes between the army and a former theology scholar turned rebel called David Yau Yau from the Murle people have devastated large parts of the troubled region.
Still reeling from more than two decades of civil war that left the region awash with guns and riven by ethnic hatred, traditional cattle raiding between rival tribes has escalated into a wave of brutal killings.
South Sudan army spokesman Philip Aguer blamed Yau Yau for the attack, which took place close to an army base near Gumuruk, a remote village in the restive Pibor region.
Amid renewed clashes between ethnic groups and government forces, UN troops have recently stepped up their patrols to deter violence and fulfil their mission of protecting civilians.
An Indian soldier was shot and wounded in Jonglei in March amid high tensions about an imminent government crackdown on rebels, while the army shot down a UN helicopter in December by mistake, killing all four Russians on board.
Hilde Johnson, the top UN official in South Sudan, warned Monday about the "destabilisation" of the region.
"Without stability and peace in Jonglei, the largest state in South Sudan, in the long run stability also in the country could be at risk," she told reporters.
"I urge the Murle, Lou Nuer and Dinka communities, their leaders, and the governments of Jonglei and South Sudan to resume and sincerely engage in peace initiatives," she added.
South Sudan's army launched the latest offensive against Yau Yau's rebels in March.
At the end of 2011, barely six months after South Sudan declared independence after decades of civil war with the north, some 8,000 armed Lou Nuer youths rampaged through Pibor County, vowing to exterminate their cattle-keeping rivals, the Murle.
The United Nations says over 600 people were killed in that attack and around 300 more in smaller reprisal attacks. Local estimates were much higher, running into the thousands.
A subsequent disarmament campaign led by security forces, mired in claims from rights groups of abuses against civilians, pushed some residents towards Yau Yau's militia.
India, a major contributor to UN peacekeeping forces around the world, has suffered losses in the past.
In 2010, rebels hacked to death three Indians in their camp in the Democratic Republic of Congo.
Akbaruddin said the Indian foreign ministry was arranging for the bodies of its peacekeepers in South Sudan to be returned home.