WFP's East and Central Africa Regional Director Valerie Guarnieri said the $57.8 million aid will be provided to about 400,000 internally displaced people, including specialised nutritional support for new mothers and young children who are most at risk from a disruption in their food supply.
"But while we and our partners are reaching more people every day, we still face difficulties accessing some areas, and the looting of food and other assets from a number of our compounds and warehouses around the country," Guarnieri was quoted as saying in a statement.
The humanitarian situation in South Sudan has deteriorated rapidly since fighting broke out in mid-December, causing not only the loss of life and displacement, but also disrupting agricultural development and humanitarian activities crucial to the survival and future livelihoods of millions.
Relief op to provide humanitarian assistance to South Sudanese
According to UN, the impacts on diversified livelihoods in four of South Sudan's 10 states are generating an alarming risk of food insecurity and malnutrition.
The crisis in the world's youngest country has forced over 200,000 people to flee their homes in search of safety, when many parts of the country should be the harvest season.
Food insecurity was a major challenge for South Sudan even before the conflict, and unrest has disrupted commercial supplies to local markets in much of the country.
Guarnieri said WFP staff have mobilised quickly to provide immediate relief to people seeking safety across South Sudan's borders.
"But all of our refugee assistance programmes in the region were already facing severe funding shortfalls before this crisis, and a new influx of refugees will strain their resources even further," Guarnieri said.
The WFP is also assisting tens of thousands of refugees who have fled across South Sudan's borders into neighbouring countries, including Uganda, Ethiopia and Kenya.