The two groups have a long and bloody history of tit-for-tat cattle raiding.

Lise Grande, the UN humanitarian co-ordinator for South Sudan, said that she was hearing reports that up to 10,000 people could have been displaced by the latest violence. 

"This particular raid comes on top of five other raids, the most recent in September. In that raid about 5,000 people were displaced and at least 10 were killed," she told Al Jazeera.

"What you have is a spiralling attack and counter-attack, this being the most recent unfortunate incident."

Rising violence

The sharp rise in tribal violence in recent months has killed more than 2,000 people, including many women and children, and displaced another 250,000 people, the United Nations has said.

in depth

  Video: New foes in South Sudan
  Video: South Sudan's mixed fortunes
  South Sudan hit by ethnic clashes

The website of the UN-funded Miraya FM radio station confirmed Monday's incident, reporting that it disrupted voter registration for national and presidential elections due to be held in April next year.

The process, which the south's leading party has said has been slow and underfunded by Sudan's National Electoral Commission, has already been hindered by tribal fighting this month.

The Sudanese People's Liberation Movement (SPLM) has also blamed at least some of the inter-tribal fighting on interference by Khartoum, which they say is arming civilians and militias to cause unrest ahead of the elections and a 2011 referendum on southern independence.

Others have said the blame should be partly put on rivalry between southern leaders, complicated by the 20-year war that often pitched southern ethnic groups against each other.