JUBA, South Sudan — More than 23,500 people have fled fighting in South Sudan's Jonglei state and sought refuge in neighboring countries of Uganda, Kenya and Ethiopia, a U.N. official said Friday.
Tim Irwin, a spokesman in South Sudan for the U.N.'s refugee agency, said majority of the refugees were fleeing to Ethiopia.
Since the beginning of May about 16,000 people have arrived in Ethiopia, 5,000 in Kenya and 2,500 in Uganda, Irwin said. The majority of those fleeing were women and children.
"Often men will stay behind to protect the land and take care of the livestock," Irwin said.
The most recent fighting started two months ago after South Sudan's government launched an operation to crush 10 months of rebellion led by David Yau Yau, a former colonel in South Sudan's military. Earlier this month 24 people died in a battle between South Sudan's military and the rebel fighters.
The U.N. said that the thousands of civilians displaced from their homes in Jonglei state's Pibor County had no access to humanitarian services.
South Sudan accuses Sudan of supporting Yau Yau's rebellion in order to block South Sudan's plans to build an oil pipeline through Jonglei state and Ethiopia. South Sudan must currently export its oil through pipelines owned by Sudan. Its plans to build a new pipeline would reduce its dependence on Sudan.
South Sudan resumed oil production in April this year, 16 months after a shutdown caused by disagreements with Sudan over oil transit fees.
Sudan has repeatedly denied having any ties to Yau Yau's rebels and has counter-accused the south of supporting rebels in Sudan's South Kordofan and Blue Nile states.
A Swiss based research group, Small Arms Survey, said in a recent report that Sudan supplied weapons and ammunition to the rebels.
Earlier this week, Sudanese President Omar al-Bashir warned his southern neighbor against supporting rebels, calling them "mercenaries" and saying he would cancel all agreements with South Sudan if it continued to support them.
"Let them drink their oil," al-Bashir said, in a characteristically fiery speech, implying he would not allow South Sudan's oil to pass through Sudan for export through the Red Sea ports.
South Sudan broke away from Sudan in 2011 under a 2005 peace treaty that ended decades of war, but disputes remain over their common border, demilitarization and sharing of oil revenues.
Jonglei state, South Sudan's largest state, has a long history of inter-communal violence mostly related to cattle-raiding. Since South Sudan declared independence from Sudan, the cattle raids have become more frequent and deadly.
Instability in Jonglei state and South Sudan as a whole is due in part to easy access to weapons. A government disarmament campaign launched in Jonglei last year ended up boosting insecurity and was accompanied by abuses against civilians, according to a United Nations report released last year.