UN warns that food aid running out for Sudanese refugees in Chad

"By December, there will be no assistance," Pierre Honnorat, Chad country director for the U.N. agency, told Reuters. "We are calling for urgent, urgent funding now."

More than 540,000 refugees have crossed from Sudan into Chad since war erupted seven months ago between the Sudanese army and the paramilitary Rapid Support Forces (RSF), according to the International Organization for Migration.

Many have fled from West Darfur, where ethnically driven violence and mass killings erupted again this month in the state capital El Geneina, pushing thousands more people to flee. Reuters has reported that between April and June this year the RSF and allied Arab militias conducted weeks of systematic attacks targeting the Masalit, El Geneina's majority ethnic African tribe.

Those who have arrived this year joined refugees and displaced people already in camps in Chad, where Honnorat described conditions as "extremely hard".

"Now it's winter, but still it's super hot," he said. "The nutrition problem is going through the roof."

"We need $25 million minimum every month to assist to provide a meal a day to those roughly 800,000 people we are trying to serve."

Sudan's conflict has also contributed to spreading hunger within the country. On Wednesday the U.N. Food and Agriculture Organization said it had distributed seeds for cereals that could feed 13 million to 19 million people, after farming was badly disrupted by the war's impact.