Rival tribes from Sudan's underdeveloped south have clashed for years in disputes often caused by cattle rustling and long-running feuds, but violence has soared this year.

The United Nations said the attacks could mar preparations for Sudan's for national and presidential elections due in April 2010.

Lise Grady, a UN Humanitarian Coordinator for southern Sudan, told Al Jazeera that “The area was not previously affected by the food crisis or inter-tribal violence and it’s not inconceivable that this is a politically motivated attack linked to the upcoming elections."

The elections are required under the 2005 peace deal that ended the north-south civil war.

Sudan is also scheduled to hold a referendum in January 2011 on whether South Sudan should become independent.