The armed forces said in a statement on Wednesday it halted talks in the Saudi city of Jeddah, accusing the other side of a lack of commitment in implementing any terms of the agreement and a continuous violation of the ceasefire.
The negotiations with the Rapid Support Forces (RSF), which began in early May, had produced a declaration of commitments to protect civilians and two short-term truce agreements, although those deals were repeatedly violated.
Eyewitnesses reported on Wednesday that the RSF had expanded its footprint within central Khartoum's Mogran district. They also reported heavy clashes across the Nile in northern Omdurman and northern Bahri through Wednesday evening.
At least 17 people were killed and 106 injured after projectiles fell on a market in a dense southern Khartoum on Wednesday, the doctors union said in a statement. It said the local Bashair hospital, one of the few still operating in the capital, was overwhelmed.
The war has killed hundreds of people, displaced more than 1.2 million inside Sudan and driven 400,000 others across borders to neighbouring states, the United Nations says.
The army, which relies on air power and artillery, and the RSF, a more lightly armed force that has dominated on the ground in Khartoum, had agreed to extend a week-long ceasefire deal by five days just before its Monday expiry.
Army chief Abdel Fattah al-Burhan, a career military officer, and RSF General Mohamed Hamdan Dagalo, a former militia commander known as Hemedti, have been locked in a battle for power since April 15. Neither side seems to have an edge.
"We do not want to use lethal force. We still haven't used our maximum strength ... We don't want to destroy the country," Burhan said in a military video released on Tuesday, speaking to cheering forces at a military base with a gun slung on his back.
"But if the enemy does not obey and does not respond we will be forced to use the strongest force we have."
The RSF said in a statement late on Tuesday it was committed to the ceasefire "despite repeated violations" by the army.
In a video released by the RSF on Wednesday, Hemedti's brother and RSF number two Abdelrahim Dagalo called on army soldiers to desert and work together with the RSF.
"Anyone who wants Sudan's best interests should leave Burhan," he said, adding that his brother was well and on the front lines.
Sudan has a history of political upheaval, coups and internal conflicts, but violence had previously hit regions far from Khartoum, which is home to millions of people.
Commenting on the Sudanese army's withdrawal from the Jeddah talks, Mohamed El Hacen Lebatt, African Union spokesperson on the crisis in Sudan, said: "It is not surprising. It happens often. We hope the mediator will succeed to bring both parties for working on an expected ceasefire."
The capital has seen widespread looting and frequent power and water supply cuts. Most hospitals have stopped functioning.
Before the ceasefire deal was renewed, an army source said the army had demanded the RSF withdraw from civilian homes and hospitals as a condition for an extension. After the five-day extension was agreed, talks continued on the truce terms.
The truce deal was brokered and is being remotely monitored by Saudi Arabia and the United States. They say it has been violated by both sides, although the truce has still allowed the delivery of aid to an estimated two million people.
