Tens of thousands of villagers in South Sudan are hiding in the bush, waiting for UN and government troops to stop a tribal conflict, which officials fear may have left scores of people dead over the weekend.

Armed youths from the Lou Nuer tribe marched on the remote town of Pibor in Jonglei state, home to the rival Murle people, who they blame for cattle raiding.

"The situation is tense as the Lou Nuer are still around Pibor," Isaac Ajiba, Jonglei's information minister, said on Monday.

Thatched huts have been burned and, according to Parthesarathy Rajendran, the head of Doctors without Borders (known by its French name Medicines sans Frontieres, or MSF) in South Sudan, thousands have been displaced, including his own staff.

"Many of our staff are in the bush and we also heard an MSF clinic has been damaged and looted," he told Al Jazeera.

"MSF is the only medical health care in the whole region, and the population is very vulnerable for all kinds of medical issues. So we are very concerned about those fleeing into the bush. They don't have access to water, medical care or food”.

The government and the UN, which has warned the violence could lead to a "major tragedy", were strengthening their forces in the area.

"We are worried about their conditions. They are without water, shelter and food. They are hiding in the bush. I think it is between 20,000 and 50,000. This is an estimate only," Lise Gande, UN humanitarian co-ordinator for South Sudan, told the Reuters news agency.

Grande said on Sunday that the number of government forces heading to Pibor was estimated at 3,000 troops and 800 police.

'Village deserted'

Al Jazeera's Haru Mutasa, reporting from a village belonging to the Murle tribe, said the situation was tense, with deserted streets.

"All you see is soldiers and guns, lots and lots of guns," she said. "It doesn't feel like a normal place.

"The UN here is trying by all means to reassure the few that are left that it's safe to return”.

Reverend Mark Akec Cien, head 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.

He said some armed men were reportedly chasing those running away.

"The Lou Nuer are there in the town, but others have left chasing after the Murle," Cien said.

More than 30 people were killed in Lukangol, about 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 said.

More than 1,000 dead

Ethnic violence, cattle raids and reprisal attacks in the vast eastern state left more than 1,100 people dead and forced about 63,000 from their homes last year, according to UN reports based on local authorities and assessment teams.

Barnaba Benjamin, South Sudan's minister of information, told Al Jazeera on Sunday that the government had taken significant steps to protect citizens.

"In the president's New Year message yesterday, he already ordered the army to co-operate with the UN peacekeeping forces to make sure that civilian lives are protected," Benjamin said.

"Secondly, Pibor town is under the full control of the government and there are no casualties at the present moment”.

Riek Machar, South Sudan's vice-president, has called on the Lou Nuer youths to pull back to their towns as per an agreement reached on December 28, which was meant to calm tensions.

The deal has yet to be implemented, and spokesmen for the Lou Nuer were quoted as saying that they would not stop their advance on the Murle people until their rivals were disarmed.

A group calling itself the Nuer Youth White Army issued a statement on December 26 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 stealing Lou Nuer cattle and killing members of their tribe since 2005, when a peace agreement ended two decades of bloody civil war and led to South Sudan's independence in 2011.

PHOTO CAPTION

A herdsman from the Nuer tribe stands among his cattle near Nyal, south Sudan. 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.

Aljazeera