South Sudan has sent troops to secure a UN base which was attacked by gunmen on Thursday, who killed at least 48 people.
Without more aid and a ceasefire to let farmers reach fields, the UN says there will be a "catastrophic decline in food security" in South Sudan.
Peace talks aimed at ending over three months of civil war in South Sudan have been paused until the end of April, say rebels.
The ANC's strong links with South Sudan could be useful in a new bid to resolve conflicts there.
The only region that is still producing oil in South Sudan two months after violence erupted has now been seized by rebels.
The ANC has decided to send its deputy president to mediate in South Sudan so that relations with the SPLM get stronger, say insiders.
East African nations have sent an advance team of monitors to observe a ceasefire agreeement between government and rebel forces in South Sudan.
The government and rebels have traded accusations of breaking the ceasefire deal intended to calm violence in South Sudan.
The UN says the South Sudanese government and opposition troops are fighting 'sporadic' battles despite a ceasefire that came into force on Friday.
President Salva Kiir's government and the rebels backing Riek Machar have signed a ceasefire deal, a "critical first step" in peace negotiations.
The brewer is among South African-based firms mugged by the country's descent into civil war.
While official estimates say 1 000 people have died in South Sudan in the surge of violence in the last month, rights groups say it could be 10 times that.
The ongoing civil war in South Sudan has already killed more than 10 000 people, and peace talks in Addis Ababa are deadlocked.
At least 200 South Sudanese civilians have died when a boat, packed with people escaping fighting between government forces and rebels, capsized.
South Sudan's loyalist troops head for the last major rebel-held town as the UN urges President Salva Kiir to release detainees loyal to Riek Machar.
Civil war looms after rebels spurn a proposal to end the violence raging across South Sudan.
South Sudan's rebels and a government delegation have begun peace talks in Ethiopia to try end fighting that has killed at least 1 000 people.
Much of the world is in turmoil at the start of this year - from increased fighting in the CAR and South Sudan to protests in Israel, Mexico and Thailand.
Delegates from South Sudan's warring factions are expected to meet for talks in the Ethiopian capital on Sunday.
Talks between South Sudan's government and rebels have been put on hold until an agenda has been drafted by negotiators and agreed on by both sides.