Saudi Arabia and the United States called on Sunday for the extension of a cease-fire deal that has brought some let-up in a six-week war between military factions, but said both sides had impeded aid efforts and were posturing for further escalation.
Clashes could be heard overnight and on Sunday in the capital Khartoum, residents said, while human rights monitors reported deadly fighting in El Fashir, one of the principal cities in the western region of Darfur.
The conflict between Sudan's army and the paramilitary Rapid Support Forces (RSF) that erupted on April 15 has left the capital reeling from heavy battles, lawlessness and a collapse in services, driving nearly1.4 million people from their homes and threatening to destabilize the region.
A week-long cease-fire brokered in Saudi Arabia and U.S.-led talks in Jeddah are due to run until Monday evening.
Both countries are remotely monitoring the truce and called on the army and the RSF to renew the "imperfectly observed" cease-fire to allow for humanitarian work.
"There were violations by both parties that significantly impeded delivery of humanitarian assistance and restoration of essential services," Saudi Arabia and the U.S. said in a joint statement.
The statement cited breaches of the truce, including air strikes and commandeering of medical supplies by the army, and the occupation of civilian buildings and looting by the RSF.
"Both parties have told facilitators their goal is de-escalation to facilitate humanitarian assistance and essential repairs, yet both parties are posturing for further escalation," it said.
The RSF has said it is ready to discuss the possibility of renewal and that it would continue to monitor the truce "to test the seriousness and commitment of the other party to proceed with the renewal of the agreement or not."
The army said it was discussing the possibility of an extension.
Nearly 350,000 people have crossed Sudan's borders since the fighting erupted, with the largest numbers heading north to Egypt from Khartoum or west to Chad from Darfur.
In Khartoum, factories, offices, homes and banks have been looted or destroyed. Power, water and telecommunications are often cut, there are acute shortages of medicines and medical equipment, and food supplies have been running low.
"We left because of the impact of the war. I have children and I fear for them because of the lack of medical treatment," one resident of the capital, 29-year-old Samia Suleiman, told Reuters from the road to Egypt.
"I also want my children to have a chance of schooling. I don't think things in Khartoum will be restored soon."
The truce deal has brought some respite from heavy fighting but sporadic clashes and air strikes have carried on.
The United Nations and aid groups say that despite the truce, they have struggled to get bureaucratic approvals and security guarantees to transport aid and staff to Khartoum and other places of need. Warehouses have been looted.
There have been increasing reports of gender-based violence, especially from people displaced within Sudan, the U.N. humanitarian office said in a statement.
Violence has flared in several parts of Darfur, already scarred by conflict and displacement, with hundreds of deaths recorded in El Geneina near the border with Chad during attacks that residents blamed on "Janjaweed" militias drawn from Arab nomadic tribes with links to the RSF.
The governor of Darfur, Minni Minawi, a former rebel whose faction fought against the militias in the Darfur conflict, said in a tweet that citizens should take up arms to defend their property.
In recent days, there has also been fighting in El Fashir, capital of North Darfur state.
One El Fashir hospital recorded three deaths and 26 injuries on Saturday, including children, according to the Darfur Bar Association, an activist group. Many more people were missing, it said.
Across the country, the health ministry has said at least 730 people have died in the fighting, though the true figure is likely much higher. It has separately recorded up to 510 deaths in El Geneina.