Sudan’s army is resisting an attempt by paramilitaries to advance towards its main air base near the capital Khartoum, residents have said.
The airfield is used by the military to carry out air strikes on the Rapid Support Forces (RSF), and was also used by foreign governments to evacuate their nationals early in the conflict.
The fighting comes despite the announcement of a new seven-day truce.
Previous ceasefires have collapsed within minutes of being called.
A US-Saudi statement said the latest truce would come into effect on Monday evening, and would be different as it provides for a “ceasefire monitoring mechanism”.
The US and Saudi Arabia have been brokering talks between the army and the RSF in the Saudi city of Jeddah for the past two weeks in an attempt to end the conflict that broke out on 15 April.
Most people I spoke to in Khartoum said a ceasefire would hold only if international monitors – backed by United Nations (UN) peacekeepers – are deployed.
In a sign of their lack of confidence in the latest ceasefire deal, bus loads of residents are continuing to flee Khartoum and its sister cities across the River Nile, Bahri and Omdurman, as there has been no let-up in the fighting.
RSF fighters in about 20 trucks are positioned east of the Nile, and are trying to cross a bridge to reach the Wadi Saeedna airfield.
The Sudanese military has retaliated by firing heavy artillery.
The battle has been going on for several days, but it has escalated.
“It feels like doomsday from early this [Sunday] morning. I think they will torture us until this ceasefire comes into effect,” said a resident in Bahri’s Khojalab suburb.
The military cannot afford to lose control of the airfield, as it is key to its military strategy of pounding the RSF from the air as it fights to regain control of Khartoum and the other two cities.
An air strike also took place in Omdurman on Sunday, and explosions could be heard in its southern areas.
Earlier, the US State Department acknowledged previous failed attempts at brokering peace in Sudan, but said there was a key difference this time.
“Unlike previous ceasefires, the agreement reached in Jeddah was signed by the parties and will be supported by a US-Saudi and international-supported ceasefire monitoring mechanism,” it said, without giving more details.
Sudan’s military said it was committed to the agreement. The RSF has not commented.
The deal also allows for the delivery of humanitarian aid.
Stocks of food, money and essentials have fast declined and aid groups repeatedly complained of being unable to provide sufficient assistance in Khartoum.
Both the regular army and the RSF have been urged to allow the distribution of humanitarian aid, restore essential services and withdraw forces from hospitals.
US Secretary of State Antony Blinken said on Twitter: “It is past time to silence the guns and allow unhindered humanitarian access.
“I implore both sides to uphold this agreement – the eyes of the world are watching.”
The war broke out following a power struggle between Sudan’s regular army chief Abdel Fattah al-Burhan and his former deputy Mohamed Hamdan Daglo, who leads the RSF.
Hundreds of people have been killed in the fighting and the UN has warned of a worsening situation in Africa’s third-largest country, where a huge number of people already relied on aid before the conflict.
On 11 May, both sides signed a commitment intended to lay the groundwork for humanitarian assistance in Sudan.
But earlier this week, UN aid chief Martin Griffiths told the AFP news agency there had been “important and egregious” violations of that agreement, which he added fell short of a ceasefire.