Sudan fighting drives 35,000 refugees into South Sudan By Hereward Holland JUBA (Reuters) - About 35,000 Sudanese refugees fleeing fighting between the army and rebels have crossed into South Sudan in the past three weeks, stretching water and aid resources to their limits, the United Nations said on Monday. Fighting erupted in Sudan's South Kordofan state in June 2011 and spread to nearby Blue Nile in September. Both states border South Sudan, which seceded from Khartoum under a 2005 agreement that ended decades of civil war. The U.N. refugee agency UNHCR said 35,000 people had arrived in South Sudan from Blue Nile and more were on the way, joining about 70,000 refugees already living in crowded camps. "This is a dramatic change in an already difficult humanitarian situation," UNHCR chief Antonio Guterres said in a statement. Not only are refugee numbers suddenly much higher, but the condition that many of these people are in is shockingly bad. Some have been eating tree leaves to survive along the way. Aid group Medecins Sans Frontieres (MSF) said 2,000 people were crossing the border every day, and camps would run out of water by the end of the week. Refugees were exhausted from spending months in the bush hiding from fighting, and also from the trek across the border which took at least two weeks, the group said. "We have a real emergency on our hands," Patrick Swartenbroekx, MSF's emergency coordinator, said in a statement. Last week, the U.N. Security Council expressed concern over the lack of access for aid and U.N. agencies to Blue Nile and South Kordofan. Khartoum accuses South Sudan of supporting rebels in both states, but Juba denies this. Reporting by Hereward Holland; Editing by Ulf Laessing and Pravin Char