The UN on Thursday called on the international community to pressure Sudan's warring parties to come to a ceasefire deal as fighting escalated with fierce clashes and air strikes.
Representatives of the military and the paramilitary Rapid Support Forces have been meeting in Jeddah since the weekend for talks mediated by the US and Saudi Arabia.
The negotiations are aimed at securing an effective truce and allowing access for aid workers and supplies after nearly four weeks of fighting in the capital and other parts of the country.
The fighting has plunged "this much-suffering country into catastrophe", UN High Commissioner for Human Rights Volker Turk said on Thursday.
Addressing a special session of the UN Human Rights Council on the situation in Sudan, he urged "all states with influence in the region to encourage, by all possible means, the resolution of this crisis".
His comments, via video message, came as fighting continued in the Sudanese capital, pushing more people to undertake dangerous journeys to safety across the country's borders.
After days of no apparent movement, a mediation source told Reuters on Wednesday that progress had been made and a ceasefire agreement was expected soon.
A second source said a deal was close. Talks continued late into Wednesday night.
US Under Secretary of State Victoria Nuland said that American negotiators were “cautiously optimistic” about securing a commitment to humanitarian principles and a ceasefire.
However, the US was also looking at appropriate targets for sanctions if the warring factions did not back this, she added.
Residents of Khartoum, which has witnessed the heaviest fighting, reported ground battles in several neighbourhoods on Wednesday.
Heavy gunfire was also reported in the north of Omdurman and the east of Bahri, two adjacent cities separated from the capital by the Nile river.
The army has been pounding targets across the three cities since Tuesday as it tries to root out RSF forces from residential areas and strategic sites seized early in the conflict.
“There's been heavy air strikes and RPG fire since 6.30am,” said Ahmed, a resident of the Bahri neighbourhood of Shambat.
“We're lying on the ground and there are people living near us who ran to the Nile to protect themselves there under the embankment.”
The conflict has created a humanitarian crisis in Africa's third-largest nation by area, displacing more than 700,000 people inside the country and prompting 150,000 to flee to neighbouring states.
It has also sparked unrest in Sudan's western Darfur region.
The UN World Food Programme said that up to 2.5 million more Sudanese were expected to fall into hunger in the coming months because of the conflict, raising the number of people suffering acute food insecurity to 19 million.
Since the battles began on April 15, the RSF have dug in across Khartoum neighbourhoods, set up checkpoints, occupied state buildings and placed snipers on rooftops.
The army has been using air strikes and heavy artillery to try to dislodge them.
