More than 650 000 refugees and asylum seekers in South Sudan risk losing food aid access within weeks due to a severe funding shortfall, potentially forcing some to return to war-torn Sudan in search of help, the UN warned on Friday.

South Sudan faces one of the world's worst hunger crises, the World Food Programme and the UN refugee agency said. More than 7.8-million people, over half the country's population, are experiencing acute food insecurity, while 2.2-million children are acutely malnourished.

It is also receiving about 3 000 refugees and returnees a week from neighbouring Sudan, where a conflict that erupted in 2023 has triggered one of the world's largest displacement crises following mass killings, rape and deliberate starvation, according to the UN.  

The last food distributions for the most vulnerable 240 000 refugees in South Sudan -- out of the 650 000 who had previously been receiving food support across the country -- would be made in September unless new funding is secured urgently, the UN agencies said.

They are the last remaining refugee families receiving food support -- which is already at half-rations -- after WFP said it was forced to progressively scale back assistance because of funding constraints. 

"This is not a future scenario. It is sadly a reality that will hold within weeks," Adham Effendi, WFP's deputy country director in South Sudan, told reporters from Juba. 

UNHCR Deputy Representative Mesfin Degefu said that if funding does not materialise, no refugees in South Sudan will be receiving food assistance from October.

Families are already reducing meals, selling belongings, withdrawing children from school and taking on debt to survive, Degefu said, while women and children face heightened risks of exploitation and abuse. Some refugees have already asked the agency to help facilitate returns, even though UNHCR does not consider conditions in Sudan safe for return.

Further cuts are expected unless it can bridge its $37-million funding gap for refugee operations between October and December. From October, food assistance for about 180 000 internally displaced people will cease, while by November some 600 000 people living in famine-risk areas could lose life-saving support, Effendi said. 

UNHCR, which has received only 28% of the $286-million it requires this year, said the funding squeeze also threatened efforts to help refugees become self-reliant through farming, vocational training and other livelihood programmes.