The UN agency estimated that 3.6 million displaced people need help in Ituri, North Kivu and South Kivu provinces, where armed groups have operated for decades.

"The living conditions for people in the camps, who have fled the fighting... have become disastrous with the arrival of the rainy season," the WFP said.

"Families are sheltering under layers of tarpaulin held up by thin branches of trees," the WFP statement said, calling the conditions "unlivable".

On top of food insecurity, "poor hygiene conditions make the sanitary crisis worse," the WFP said, adding "cholera is rife in the camps."

"Due to the poor-quality road infrastructure, the heavy rainfall has blocked deliveries of food."

Added to this was the "insecurity" created by armed groups which affects access to the main supply routes, it added.

The WFP said it had increased capacity in recent months but "resources are lacking", particularly for "host communities" to help the displaced.

The WFP said that $629.7 million was need very urgently to maintain and increase vital aid to the three provinces.