The United Nations has warned 800,000 people may flee Sudan as rival military factions battle in the capital despite a supposed ceasefire.
Hundreds of people have been killed and thousands wounded over 16 days of violence since disputes between the Sudanese Army and the paramilitary Rapid Support Forces (RSF) erupted into conflict on April 15.
There seems little prospect of a quick resolution to the crisis, which has unleashed a humanitarian disaster, damaged swathes of Khartoum, risked drawing in regional powers, and reignited conflict in the Darfur region.
Both sides agreed on Sunday to extend a much-violated truce by 72 hours, and the UN told Reuters they might hold truce talks in Saudi Arabia. But air strikes and artillery rang out on Monday as smoke hung over Khartoum and neighbouring cities.
UN refugee deputy chief Raouf Mazou said his agency was planning for an exodus of 815,000 people including 580,000 Sudanese and foreign refugees now living in the country.
Some 73,000 had already left Sudan, he said.
Sudanese who ventured onto the streets were shocked by the transformation.
"We saw dead bodies. The industrial area, that was all looted. We saw people carrying TVs on their backs and big sacks looted from factories," resident Mohamed Ezzeldin said.
Many fear for their lives in the power struggle between the army chief and RSF head, who had shared control of government after a 2021 coup but fell out over a planned transition to civilian rule.
Tens of thousands of Sudanese have fled their homes, some congregating in hubs such as Atbara north-east of Khartoum while they work out plans or head for the Egypt and Chad borders.
At least 528 people have been killed and 4,599 wounded, according to the health ministry.
The United Nations has reported a similar number of dead but believes the real toll is much higher.
"Without a quick resolution of this crisis we will continue to see more people forced to flee in search of safety and basic assistance," Mr Mazou told a member state briefing in Geneva on Monday.
At the same briefing, the United Nations resident and humanitarian coordinator in Sudan, Abdou Dieng, warned that the humanitarian crisis was turning into a "full-blown catastrophe" and the risk of spillover into neighbouring countries was worrying.
"It has been more than two weeks of devastating fighting in Sudan, a conflict that is turning Sudan humanitarian crisis into a full-blown catastrophe," Mr Dieng said via video link.
Foreign governments have pulled out their citizens over the past week in a series of operations by air, sea and land, though several countries have ended efforts.
Those remaining face hardship and danger.
"I show up to work for two or three hours then I close up because it's not safe," said Abdelbagi, a barber in Khartoum who said he had to keep working as prices were rising.
Egypt said 40,000 Sudanese had crossed its border, while others have gone to Chad, South Sudan, and Ethiopia, or journeyed over the Red Sea on evacuation boats.
Power and water supplies are uncertain, there is little food or fuel, most hospitals and clinics are out of service and soaring transport costs are making it ever harder to leave.
The UN and other aid organisations have cut services, though the World Food Programme said it was resuming operations in more secure areas on Monday after staff were killed early in the war.
The UN fears for the war's impact both on Sudan and the broader region, said Martin Griffiths, a senior official for humanitarian and emergency relief matters, warning the country was at "breaking point".
"The scale and speed of what is unfolding in Sudan is unprecedented," said Mr Griffiths, who will visit Sudan on Tuesday.
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