The United Nations has accused rebel forces in South Sudan of attacking a town in Upper Nile State in what it said was the most serious resumption of hostilities since leaders of warring factions made fresh commitments in May to adhere to a peace agreement.
Fighters loyal to rebel leader Riek Machar struck Nasir — a town retaken by government forces two months ago — about 300 miles north of Juba and close to South Sudan's border with Ethiopia. It was not immediately clear if there were casualties.
The U.N. Mission in South Sudan (UNMISS) laid the blame squarely with Machar’s forces for the renewed fighting. "The attack is a clear violation of the Cessation of Hostilities Agreement," it said.
But a spokesman for Machar's forces, Lul Kuang, defended their moves as an act of "self defense" after what he described as several government attempts to arrest their military commander.
"The fall of Nasir now paves the way for military resources to be refocused on Poloich Oil Fields, Maban and Malakal", Kuang said in a statement, referring to the main remaining oil field still in activity.
South Sudanese army spokesman Philip Aguer denied Nasir had fallen, describing fighting as "still ongoing.” Aguer said army forces had staged nine offensives on Nasir on Sunday.
Only days earlier, mediators had pressed the rival sides to resume peace talks being held in Ethiopia, or face increased sanctions.
Those talks, which are designed to lead to a transitional government but have yielded little progress so far, were moderated by the Intergovernmental Authority on Development (IGAD), an East African trade bloc whose stated mission includes promoting peace and security among its member states.
"It is deplorable that this major attack comes at a time when intensive efforts are underway by mediators of the Intergovernmental Authority on Development (IGAD) to convince all parties to resume the suspended peace talks in Addis Ababa," UNMISS acting head Raisedon Zenenga said.
IGAD also released a statement condemning the attack, saying, “While the casualties of this attack are yet to be assessed, the mediation team is saddened by the continued loss of lives not only of combatants but of vulnerable groups like women and children.”
South Sudan, the world's youngest nation, marked only the third anniversary of its independence this month under the shroud of a war that has inflamed ethnic hatred and brought its people to the brink of famine.
The conflict has raged since mid-December when presidential guards loyal to Kiir clashed with troops supporting Machar, who fled to the bush and rallied a huge rebel army. Kiir has accused Machar of attempting a coup.
Fighting had abated since May in part due to heavy rains and poor roads that hampered troop and equipment movements. However, an estimated 1.5 million people have been displaced over the course of the conflict, according to U.N. figures, and thousands more killed, including civilians massacred indiscriminately in hospitals and churches and dumped in mass graves.
Al Jazeera and wire services