The warring parties in Sudan's civil war have traded blame for an attack on a UN World Food Programme convoy trying to bring aid to an area of North Darfur where fighting and blockades have led to deadly hunger.

The convoy was hit north of the city of al-Fashir, the army's only holdout in the wider Darfur region where an estimated 300 000 remaining residents have been subject to a long siege by the rival Rapid Support Forces as fighting rages.

Aid has frequently come under fire and been blockaded by both sides in the war, which erupted from a power struggle in April 2023 and has caused what the UN has called the world's biggest humanitarian crisis.

"On 20 August, a WFP convoy of 16 trucks carrying life-saving food aid for the most vulnerable populations in Alsayah village came under attack near Mellit, a famine-affected area in North Darfur," WFP said in a statement, adding that three of the trucks caught fire but no one was hurt.

The RSF accused the Sudanese army of hitting the convoys as part of a drone attack on Mellit market and other areas. The army later said in a statement that this was a fabrication to distract from what it termed the RSF's crimes in al-Fashir.

The RSF's siege of al-Fashir has cut off supplies and driven up prices. Experts determined that famine had taken hold in parts of the area last year.

Civilians have come under artillery bombardment, drone strikes, as well as direct attacks. Camps for displaced people have been repeatedly attacked. Last week, local activists said more than 40 people were killed, including by direct fire, when RSF soldiers entered the Abu Shouk camp in the north of the city. The RSF denied responsibility for the deaths.

Those who leave al-Fashir face RSF checkpoints and have come under attack, including sexual assaults.

Some 70 trucks of supplies are waiting in the RSF-controlled city of Nyala to get to al-Fashir, but security guarantees were needed as humanitarian workers were coming under attack, said Edem Wosornu of UN humanitarian agency OCHA.

"We have food, we have medical supplies, we have kits for gender-based violence, we have life-saving equipment that will save lives," she said.

US senior Africa advisor Massad Boulos, who last week called on the RSF to ensure aid reaches al-Fashir, condemned the convoy attack.