GENEVA: Thousands of children are facing an imminent risk of death as malnutrition rates skyrocket in the besieged city of al-Fashir in Sudan's Darfur region, four United Nations agencies said on Thursday.

More than a quarter of a million civilians, about half of them children, have been cut off from food and healthcare in the city during a 16-month-old standoff, the agencies said.

"Health facilities have collapsed, and thousands of children suffering from severe acute malnutrition are now without treatment," the agencies said.

Famine-stricken al-Fashir is the Sudanese army's last holdout in the vast, western region as it battles the paramilitary Rapid Support Forces in a civil war that began in April 2023.

The International Organization for Migration (IOM), refugee agency UNHCR, children's organisation UNICEF and the World Food Programme said their representatives had seen widespread devastation in Darfur and other parts of the country during visits.