Nyaguol Bayak wants revenge: her three children were slaughtered when gunmen attacked in this remote and impoverished eastern region of South Sudan.

Still reeling from more than two decades of civil war that left this region awash with guns and riven by ethnic hatred, traditional cattle raiding between rival tribes has escalated into a wave of brutal killings.

In the dusty village of Walgak, some 350 kilometres (220 miles) north of Juba, people are bitter over a massacre in February in which over 100 people were shot, speared or hacked to death.

"I want to mobilise my people to go after those who killed them," Bayak said.

Few here in this remote village appear willing to listen to government and international messages about the need for reconciliation, and warnings are growing that militia forces are gathering once again for a large scale revenge attack.

More than two years since South Sudan voted to become the world's youngest nation, few in troubled Jonglei state are seeing the benefits of peace.

Bloody clashes between the army and a former theology scholar turned rebel called David Yau Yau -- who Juba accuses of taking arms from foes in north Sudan -- have devastated large parts of this troubled region.

The Lou Nuer people in Walgak, attacked as they moved cattle herds to find fresh pastures, blame the rival minority Murle tribe -- the same people Yau Yau's soldiers come from -- for the massacre.

"The situation is deteriorating", said Hilde Johnson, the top UN official in South Sudan, warning there are "signs of Lou Nuer mobilisation complicated by an element of rebellion with David Yau Yau forces."

UN peacekeepers, stationed in small numbers across a vast land with limited mud roads impassable for months during heavy rains, are preparing "contingency plans", she added.

But in previous attacks, the few peacekeepers did little to halt the killings.

-- Revenge attacks target women and children --

Yau Yau launched his rebellion in 2010 after alleging state elections were rigged, later agreed to an amnesty, but then returned to war.

His agenda is unclear, but several hundred Murle are believed to have flocked to his army after a spate of massacres and an army-led disarmament process marred by abuses against civilians.

The Murle took arms from Sudan during the 1983-2005 civil war that led to a referendum on South Sudan's independence, and are still viewed with suspicion by other groups in the region.

"I want them to be killed," said 17-year-old Nyapuoch Khor. "They don't want to put their guns down and they don't want to listen to the government," she added.

However, in Yau Yau's home region of Pibor, some 180 kilometres (110 miles) south of Walgak, the Murle say they are simply defending themselves.

In late 2011, up to 8,000 Lou Nuer youths -- a militia known as the White Army -- armed with automatic rifles and rocket propelled grenades went on a rampage targeting the Murle, killing scores, torching villages, stealing cattle and abducting women and children.

"There is a major risk that the cycle of violence starts again," Johnson added.

Security sources say that there are links between the army and militia forces on all sides.

The Small Arms Survey, a Swiss-based independent research group, said the Lou Nuer attacks in 2011 marked an "unprecedented level of organisation and scale of violence", noting that the youths were armed with weapons believed to have come from both rebel sources and security forces.

This week, Britain, Canada, France, The Netherlands, Norway and the United States issued a joint warning about the situation in Jonglei, "where the rule of law is scarce and civilian lives are endangered."

South Sudan's army has been battling Yau Yau's forces for months, with spokesman Philip Aguer claiming troops had last week killed scores of rebels and captured an airstrip where "secret planes carrying weapons from Khartoum" had landed.

Khartoum rejects claims it backs the rebels, and when South Sudan's army shot down a helicopter in December it believed was supplying insurgents, it turned out to be a United Nations helicopter. Four Russians on board were all killed.

Although impossible to verify victorious army claims of rebel deaths, eyewitnesses have seen truckloads of wounded soldiers leaving Juba airport in recent days.

As warnings grow of the risk of further violence, the numbers of refugees fleeing into neighbouring Ethiopia and Kenya grows too.

Both Human Rights Watch and Amnesty International have condemned a string of reported abuses -- including shootings, torture and rape -- as security forces crack down on those seen to support the rebels.

Doctors Without Borders (MSF), whose clinics were attacked and looted last year, has documented multiple cases of rape, and warns that women and children have been deliberately targeted.

Those it has treated recounted stories including babies speared or hurled into huts set on fire.