A 24-hour ceasefire has agreed between Sudan's army and paramilitaries has been broken.
A witness in capital Khartoum told Sky News fighting had continued after the deal was to come into effect at 6pm local time.
Ongoing violence that has killed at least 185 people since Saturday.
More than 1,800 people have also been injured, according to the United Nations figures, in a conflict that has seen air and artillery strikes.
According to the Sudan Doctors' Syndicate, 144 of the casualties are civilians. Those living in cities, including the capital Khartoum, have been forced to hide at home.
Clashes have continued despite calls from the US and others to stop, while Egypt and the United Arab Emirates had been trying to broker a ceasefire.
It comes after a day after a US embassy convoy was fired upon in what Secretary of State Antony Blinken called a "reckless" and "irresponsible" incident.
He phoned Rapid Support Forces (RSF) leader General Mohamed Hamdan Dagalo, known as Hemedti, and General Abdel Fattah al-Burhan, the country's de facto president, to warn that any danger posed to US diplomats was unacceptable.
The people in the diplomatic convoy are safe, Mr Blinken said, adding: "We have deep concerns, of course, about the overall security environment as it affects civilians, as it affects diplomats, as it affects aid workers."
Tensions had been escalating after a power pact between Hemedti and General al-Burhan broke down. The violence has once again seen Sudan' civilians caught in the crossfire.
Their struggle for control has derailed a shift to civilian rule and raised fears of a wider conflict.
While the army is larger and has air power, the RSF is widely deployed inside neighbourhoods of Khartoum and other cities, giving neither faction the edge for a quick victory.
Speaking to Sky News, General al Burhan said he was open to negotiations as the fighting continues.
"If negotiations will restore the country and are fair then it's possible," he added.
General al Burhan heads a ruling council installed after a 2021 coup and the 2019 ousting of veteran leader Omar al Bashir during mass protests.
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Khartoum is a city unused to violence, but on Monday smoke hung over the capital as residents reported a clamour of airstrikes, artillery fire and shooting that shut hospitals.
The conflict in the capital and its adjoining sister cities of Omdurman and Bahri since Saturday is the worst in decades.
The fighting has also spread to the war-wrecked western Darfur region, and areas of northern and eastern Sudan, near the borders with Egypt and Ethiopia.
