The U.N. Mission in South Sudan said ethnic clashes have been a security issue since December. Conflict in Jonglei, triggered by cattle raids, claimed at least 1,000 lives in recent months. Most of the victims are women and children.
Gen. Kuol Diem Kuol from the Sudan People's Liberation Army, South Sudan's military, said a regional conference aimed at a peaceful settlement to the issue was a "last chance" effort.
"The SPLA will not allow killing of children to continue," he was quoted by the independent Sudan Tribune as saying. "SPLA will start killing raiders if these acts continue."
South Sudan gained independence in July a part of an agreement that brought an end to civil war in Sudan. Clashes with Sudanese forces, border skirmishes and ethnic violence threatens the peace, however.
South Sudanese officials met in London with British Foreign Secretary William Hague to discuss security in the region.
"I underlined the U.K.'s continued commitment to helping both Sudan and South Sudan achieve security and prosperity for their people, in the context of a comprehensive settlement of their disputes," Hague said.