Millions of people displaced by Sudan's civil war risk being left without emergency shelter as funding shortfalls deplete aid stocks, the UN refugee agency UNHCR and the International Organization for Migration said on Friday.

The agencies said an estimated 15.4-million people across Sudan urgently need emergency shelter and basic household items, but funding constraints mean humanitarian agencies can prioritise assistance for only about 10% of those in need.

So far, 936 000 people have received assistance, leaving a large gap between needs and available resources, according to a joint statement.

Sudan remains the world's largest displacement crisis more than three years after war broke out in 2023, when the Sudanese army and the paramilitary Rapid Support Forces clashed over issues including how to integrate their forces in a planned transition to civilian rule.

Around 8.6-million people remain displaced within the country, while more than 4.6-million have fled across borders. More than 5.2-million people have also returned to their areas of origin, often finding homes, infrastructure and basic services destroyed.

Speaking from Khartoum during a UN briefing in Geneva, IOM Sudan chief Mohamed Refaat said the agency was struggling to maintain operations as resources dwindled.

"Just this year, IOM was able to distribute more than 40 000 tons, but our warehouses are completely empty now," he said.

Refaat said the number of internally displaced people could rise again despite recent returns. He said agencies had already scaled back ambitions because of limited funding.

"We decided to serve only one out of ten. But even within the one out of ten, we could reach only 900 000 people with what we had," he said.

The agencies called for urgent funding to replenish emergency stocks and prevent further deterioration in conditions for displaced Sudanese.