A U.N. official in South Sudan says more than 120,000 people need humanitarian aid because of a wave of ethnic clashes in a remote and volatile region. Lise Grande says that battles in Jonglei state are straining international relief efforts. The U.N. mission originally projected that the same number of people displaced in South Sudan last year -- 350,000 -- would be displaced in 2012. But Grande says 120,000 people have already been affected. The fighting in Jonglei state is between two cattle raiding tribes. The Lou Nuer sent columns of warriors to attack the Murle in late December and early January. The Murle have since carried out a string of revenge attacks.