The Sudan doctors' union said late on Sunday that El-Fasher hospital had reported "six deaths and 61 injuries ... following clashes" between the army and the RSF.

Separately, the local resistance committee, part of a nationwide pro-democracy organisation marshalling aid across Sudan, said earlier that the number of deaths had reached nine.

The clashes came as France was preparing an international humanitarian conference for war-battered Sudan and its neighbours on Monday.

Fighting broke out on April 15 last year between Sudan's regular army, headed by the country's de facto leader Abdel Fattah al-Burhan and the RSF paramilitaries of his former deputy and ally Mohamed Hamdan Daglo.

The western region of Darfur, about the size of France and home to a quarter of the country's 48 million people, has been the site of horrific violence, with reports of mass ethnic-based killings.

El-Fasher in North Darfur State, the last state capital not under RSF control in the vast region, had been a site of comparative stability and a key humanitarian refuge before violence broke out there too on Sunday.

The city's relative peace, which the UN described as the "fragile status quo", was abruptly broken when "clashes took place in the countryside west" of the city, a human rights activist told AFP last week on condition of anonymity.

Unrest has soared since the two most powerful armed groups in the area -- led by Darfur governor Mini Minawi and Sudan's finance minister Gibril Ibrahim -- pledged to fight alongside the army.

The local resistance committee said an RSF-affiliated armed group had set six villages in the area on fire Sunday night.

Earlier this month, military jets conducted strikes that "failed to avoid civilian locations and killed dozens of civilians", the US envoy for Sudan Tom Perriello said.

Across the country, the year-old war has killed many thousands, including 10,000 to 15,000 people in a single West Darfur town, UN experts found.

It has also pushed Sudan to the brink of famine, devastated already fragile infrastructure and driven more than 8.5 million people from their homes.