Northern parts of Kharthoum reportedly remained the scene of conflict as a week-long cease-fire brokered in Saudi Arabia and U.S.-led talks in Jeddah is due to expire on Monday evening.
Both countries are remotely monitoring the truce and called on the army and the Rapid Support Force to renew the "imperfectly observed" ceasefire to allow for humanitarian work.
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.
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.
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.
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.
"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."
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.