Thousands of villagers in South Sudan hid in the bush on Monday, waiting for UN and government troops to stop a cattle vendetta which officials fear may have left scores of people dead over the weekend.
A column of some 6000 armed youths from the Lou Nuer tribe marched on the remote town of Pibor in troubled Jonglei state, home to the rival Murle people, who they blame for cattle raiding and have vowed to exterminate.
They burned thatched huts and looted a hospital run by Doctors Without Borders, the worst flare-up in a dispute that has already left more than 1,=000 dead in recent months and threatens to destabilize the six-month-old country.
"The situation is tense as the Lou Nuer are still around Pibor," said Jonglei state information minister Isaac Ajiba, adding that army reinforcements are still on their way to the remote settlement.
"They (the army) are yet to arrive but we hope to have the reinforcements there soon… We have reports of several casualties, but at present the exact numbers are not verified," Ajiba added.
The government and the United Nations — which has warned the violence could lead to a "major tragedy" — are beefing up their forces in the area.
UN peacekeepers are on high alert and working to evacuate the most vulnerable civilians from the area.
Reverend Mark Akec Cien, general secretary of the Sudan Council of Churches, an umbrella organization with members across the area, said they had reports of many killed and wounded in the clashes.
"The situation is very bad, there have been heavy casualties, and the Murle have fled out of the town," Cien said from South Sudan's capital Juba, adding that some gunmen were reportedly chasing those running away.
"The Lou Nuer are there in the town, but others have left chasing after the Murle," he added.
Over 30 people were killed in Lukangol, some 30km north of Pibor where Lou Nuer fighters attacked last week, burning the settlement to the ground, Cien said, quoting reports from the ground.
"There are several wounded too, some say over 80, and that does not include the Lou Nuer, as they are not saying how many may be casualties from the fighting," he added.
Ethnic violence, cattle raids and reprisal attacks in the vast eastern state left over 1100 people dead and forced some 63,000 from their homes last year, according to UN reports based on local authorities and assessment teams.
Lise Grande, the UN humanitarian coordinator for South Sudan, said Sunday that the number of government forces heading to Pibor was estimated at 3000 troops and 800 police.
Doctors without Borders, the only organization providing health care in the area, said its staff had mostly fled into the bush.
A group calling itself the Nuer Youth White Army issued a statement on 26 December vowing to "wipe out the entire Murle tribe… as the only solution to guarantee long-term security of Nuer cattle."
The group accuses the Murle of raiding Nuer cattle and killing their people since 2005, when a peace agreement ended two decades of civil war and led to South Sudan's independence last year.
Many groups accuse the Murle of abducting children from neighboring tribes, with the boys used to herd cattle, and girls valued for the future dowry of cows they will earn, communities say.