Some 200 civilians have been wounded in ongoing clashes between rival tribes in South Sudan. U.N. humanitarian coordinator in South Sudan, Toby Lanzer said in a statement on Sunday that the most critically wounded are now being treated in the capital of Jonglei state, where there is a rebel insurgency against the central government. Lanzer's statement said fighting in Pibor has forced thousands to flee into the bush. It urged all the warring groups to ``ensure that aid organizations continue to have impartial, unconditional and unhindered access to civilians in need throughout the state. Instability in Jonglei and South Sudan as a whole is due in part to easy access to weapons. According to a United Nations report released last year, a government disarmament campaign launched in Jonglei last year ended up boosting insecurity and was accompanied by abuses against civilians. The humanitarian coordinator is now urging the central government and local officials to stop ``the cycle of violence'' that has killed many people and displaced thousands.