In a statement, the WFP said it had launched an air operation from a new base at El Obeid in northern Sudan, to supplement existing air and road shipments from Kenya and Uganda.

Food shipments will be made by road and air

It said 16,000 tonnes of food had been airlifted to the worst-hit region of Bahr al-Gazal on Saturday.

Further airdrops were carried out to supply another 25,000 people in the Panthou area on Sunday.

Aid agencies estimate that the number of people needing food in southern Sudan is three times greater than first thought.

The UN estimates that 2.2 million southern Sudanese, most living in areas controlled by rebel movements but others in government-held areas, are in need of food.

A WFP appeal to donors for $65.8m to support its emergency programmes in the Sudan over the coming year has so far produced only $15.4m, UN officials said.