More than 500 people have been killed since battles erupted on April 15 between the forces of army chief Abdel Fattah al-Burhan and his number two Mohamed Hamdan Daglo, who commands the paramilitary Rapid Support Forces (RSF).

They have agreed to multiple truces but none has effectively taken hold as the number of dead civilians continues to rise and chaos and lawlessness grip Khartoum, a city of five million people where many have been cloistered in their homes lacking food, water, and electricity.

Tens of thousands of people have been uprooted within Sudan or embarked on arduous trips to neighbouring Chad, Egypt, South Sudan and Ethiopia to flee the battles.

"There is no right to go on fighting for power when the country is falling apart," UN chief Antonio Guterres told Saudi-owned Al Arabiya television.

The latest three-day ceasefire -- due to expire at midnight (2200 GMT) Sunday -- was agreed Thursday after mediation led by the United States, Saudi Arabia, the African Union and the United Nations.

"We woke up once again to the sound of fighter jets and anti-aircraft weapons blasting all over our neighbourhood," a witness in south Khartoum told AFP.

Another said fighting had continued since the early morning, especially around the state broadcaster's headquarters in the capital's twin city of Omdurman.

Other witnesses reported exchanges of machine gun fire across the Blue Nile in Khartoum North, while the sound of gunfire rang out in Burri in the east of the city.

Smoke drifted over the area around Khartoum airport.

- Trading blame -

As battles raged, the rival generals -- who seized power in a 2021 coup -- took aim at each other in the media, with Burhan branding the RSF a militia that aims "to destroy Sudan" and Daglo calling the army chief "a traitor".

Guterres threw his support behind African-led mediation efforts.

"My appeal is for everything to be done to support an African-led initiative for peace in Sudan," he told Al Arabiya.

The violence has killed at least 528 people and wounded 4,599, the health ministry said Saturday, but those figures are likely to be incomplete.

About 75,000 have been displaced by the fighting in Khartoum and the states of Blue Nile, North Kordofan, as well as the western region of Darfur, the UN said.

The fighting has also triggered a mass exodus of foreigners and international staff.

On Saturday, a ferry with around 1,900 evacuees arrived at a Saudi naval base in Jeddah, after crossing the Red Sea from Port Sudan in the latest evacuation to the kingdom by sea.

They were among almost 4,880 people who have been brought to safety in the kingdom, the Saudi foreign ministry said.

A US-organized convoy carrying American citizens, local staff, and nationals from allied countries arrived in Port Sudan Saturday to join the exodus across the Red Sea, the State Department said.

The Pentagon said it had "deployed US intelligence, surveillance and reconnaissance assets to support air and land evacuation routes which Americans are using."

Britain said it was ending its evacuation flights, after airlifting more than 1,500 people this week.

The World Food Programme has said the violence could plunge millions more into hunger in a country where 15 million people -- one-third of the population -- already need aid to stave off famine.

About 70 percent of hospitals in areas near the fighting have been put out of service and many have been shelled, the doctors' union said.

- 'Incredibly worried' -

In West Darfur state, at least 96 people were reported to have been killed in the city of El Geneina this week, the UN said.

"What's happening in Darfur is terrible, the society is falling apart, we see tribes that now try to arm themselves," Guterres said.

Doctors Without Borders (MSF) said there were reports of widespread looting, destruction, and burning of property, including at camps for displaced people.

MSF deputy operations manager for Sudan, Sylvain Perron, said the fighting had forced the agency to stop almost all its activities in West Darfur.

"We are incredibly worried about the impact this violence is having on people who have already lived through waves of violence in the previous years."

Darfur is still reeling from a war that erupted in 2003 when then hardline president Omar al-Bashir unleashed the Janjaweed militia, mainly recruited from Arab pastoralist tribes, against ethnic minority rebels.

The scorched-earth campaign left at least 300,000 people dead and close to 2.5 million displaced, according to UN figures, and saw Bashir charged with war crimes, crimes against humanity and genocide by the International Criminal Court.

The Janjaweed later evolved into the RSF, which was formally created in 2013.

The 2021 coup that brought Burhan and Daglo to power derailed the transition to elective civilian rule launched after Bashir was ousted following mass protests in 2019.

The two generals later fell out, most recently over the planned integration of the RSF into the regular army.