Rome:
The United Nations food agency on Saturday warned South Sudan risked famine due to the conflict between the government and rebels and appealed for free access for humanitarian supplies along roads and rivers.
"Some areas of the country appear to be at high risk of famine in the coming months," the Rome-based Food and Agriculture Organisation (FAO) said in a statement following an assessment carried out in April and May.
With a ceasefire due to come into force on Saturday, the FAO said hunger had been caused by "displacement, destroyed markets and disrupted livelihoods" since fighting first broke out in December last year.
"There is a small window of opportunity to prevent this terrible crisis from deteriorating into catastrophe," said Sue Lautze, FAO's head of office in South Sudan.
The UN's World Food Programme (WFP), also based in Rome, said that following the report it would expand aid supplies to reach 3.2 million people this year.
It said the situation was particularly "alarming" in areas isolated by the conflict, including several counties of Unity State "where up to three quarters of the population currently face severe hunger".
Jonglei and Upper Nile are also badly hit, it said.
"A hunger catastrophe can still be avoided, but humanitarian agencies must be allowed to reach tens of thousands of people in need before it's too late," Mike Sackett, WFP country director, said in a statement.
"It is absolutely critical to stop fighting and other obstacles that prevent life-saving aid deliveries."
WFP said its supplies had reached 700,000 people so far including by boat and with airdrops but it required more donor support to ramp up assistance further.
"The agency currently has a funding shortfall of $261 million (190 million euros)," it said.
A ceasefire between South Sudan's government and rebels was due to come into effect Saturday following a deal to end a brutal five-month war that has pushed the country to the brink of genocide and famine.
FAO explained that the food security crisis was spreading westwards into areas that had been less affected earlier this year, hampering farming activities like herding, planting fields and fishing.
Lautze said aid agencies should be given humanitarian access, including official permission to access barge corridors, the removal of arbitrary checkpoints and an end to the commandeering of emergency food supplies.
FAO said only 54 percent of its $77 million appeal for helping farmers in South Sudan had been funded.