By Andrew Green
JUBA (Reuters) - Fighting between South Sudan's army, rebels and rival tribes has sent thousands of people fleeing into the bush in the east of the country, U.N. and aid officials said on Sunday.
South Sudan's army is facing a rebellion from local politician David Yau Yau in the vast Jonglei state, and new clashes have broken out between rival Lou Nuer and Murle tribes.
Western powers are worried the violence will escalate into full civil war, undermining stability in the young African country, which is awash with arms after decades of conflict with Khartoum that led to its secession from Sudan in 2011.
The United Nations said thousands of people were hiding in the bush outside Pibor town in Jonglei to escape from conflict between the army and Yau Yau, who says he is fighting corruption, army abuses and one-party rule in South Sudan.
"The communities are in urgent need of medical attention," Toby Lanzer, the U.N. Humanitarian Coordinator in South Sudan, said in a statement.
At least 200 wounded people had arrived in the Jonglei town of Manyabol after fleeing clashes between the Lou Murle and Murle, the U.N. said. Bringing in aid was difficult as the rainy season had made overland travel impossible.
A United Nations source said armed Lou Nuer youth had attacked at least three Murle villages in the past two weeks. Fighters loyal to Yau Yau, who is popular with his Murle tribe, had come to help fight back.
South Sudan's army spokesman Philip Aguer confirmed there had been new fighting in Jonglei but gave no details.
South Sudan accuses Khartoum of supplying Yau Yau with weapons. Diplomats say the claims are credible but South Sudan's army is also fuelling dissent with abuses such as rape, killings and torture committed during a state disarmament campaign.
Last week, the United States, South Sudan's biggest ally, said Juba was not doing enough to protect civilians and urged the army to stop attacking U.N. staff and looting aid agencies.
South Sudan has struggled to turn its army, a loose group of former guerrillas formed during the civil war, into a professional force.
A cycle of tribal violence has killed more than 1,600 people in Jonglei since South Sudan's secession, hampering plans to explore for oil with the help of France's Total and U.S. firm Exxon.
(Writing by Ulf Laessing in Cairo; Editing by Andrew Roche)