Warplanes on bombing raids drew heavy anti-aircraft fire over Khartoum on Saturday as fierce fighting between Sudan's army and the Rapid Support Forces (RSF) entered a third week, violating a renewed truce. 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 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 neighboring 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 Al Arabiya television. The latest three-day ceasefire -- due to expire at midnight Sunday (2200 GMT) -- 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 neighborhood," a witness in south Khartoum told AFP. Another witness said fighting had continued since the early morning, especially around the state broadcaster's headquarters in the capital's twin city of Omdurman. Smoke drifted over the area around Khartoum airport on Saturday afternoon. Trading blame UN head of mission Volker Perthes said Friday that tensions between the rival generals had been "clear" before the fighting broke out. But "there was no... early warning that battles will begin on the morning of" April 15, Perthes told Al Jazeera television, adding that efforts had been made to de-escalate the tensions. He said the two sides were meant to meet on the morning of April 15 but "this did not happen." As battles raged, the two 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 512 people and wounded 4,193, according to the health ministry, 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 Sudanese, 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. An Emirati evacuation plane arrived from Sudan on Saturday carrying citizens and nationals from 16 countries, the United Arab Emirates said. They are among almost 4,880 people who have been brought to safety in the Kingdom, the Saudi foreign ministry said. Britain said it would end its evacuation flights on Saturday, after airlifting more than 1,500 people this week. The World Food Program 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, said the doctors' union. '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," said Guterres. 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." 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.