Geneva - Looters in South Sudan stole UN food aid that would have fed over 220 000 people for a month, the World Food Programme said Friday.
The UN agency's spokesperson Elisabeth Byrs said: "Humanitarian access and looting of food stocks are major concerns.
"As a result of looting reported at WFP facilities around the country, we currently estimate 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.
Byrs said the WFP was trying to bring in more food, possibly through airlifts.
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.
Byrs said that it had been able to help 178 000 people so far.
"This number is rising almost daily, despite intense security and logistical challenges that have severely complicated the response," Byrs said.
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.
Despite a ceasefire signed in Ethiopia late on Thursday, the rebels on Friday accused the army of attacking their positions, though the military denied the claims.