Looters in South Sudan have stolen UN food aid that would have fed over 220,000 people for a month.

Looters in South Sudan have stolen UN food aid that would have fed over 220,000 people for a month, the World Food Program said Friday.

"Humanitarian access and looting of food stocks are major concerns," the UN agency's spokeswoman Elisabeth Byrs told reporters.

"As a result of looting reported at WFP facilities around the country, WFP currently estimates that we may have lost more than 3,700 metric tons of food enough to feed more than 220,000 people for a month."

Among the hardest-hit locations was northern town Malakal, the capital of oil-producing Upper Nile state.

Aid agencies have been scrambling to deal with a ballooning humanitarian crisis in South Sudan, already one of the world's poorest nations, after fighting erupted in December.

The country, which won independence from Sudan in 2011 after decades of warfare, has been gripped by clashes between government loyalists and a loose coalition of army defectors and ethnic militia.

Byrs said that the UN hoped the ceasefire would hold, enabling aid agencies to provide urgently-needed relief to the population.

Adrian Edwards, spokesman for the UN high commissioner for refugees, said Friday that more than 100,000 South Sudanese have sought refuge in neighboring Uganda, Ethiopia, Kenya and Sudan.

South Sudan is also host to 230,000 refugees, mostly from Sudan, the bulk of whom relied on aid to survive even before the fighting began.