The main South Sudanese rebel group, SPLM-In Opposition, is calling for humanitarian corridors to allow aid to get through to areas it controls.
Famine was declared in part of the country last month. The rebels and the United Nations have accused the government of restricting humanitarian access to rebel-controlled areas, a charge the authorities have denied.
The rebel group wants an intervention similar to Operation Lifeline Sudan, a huge cross-border aid programme that helped southern Sudanese during the war that led to independence from Sudan.
Source: BBC