A US-brokered ceasefire between Sudan's warring generals brought some calm to the capital, but witnesses reported fresh air strikes and paramilitaries claimed to have seized a major oil refinery and power plant.
"The pause was not fully upheld, with attacks on headquarters, attempts to gain ground, air strikes, and explosions in different areas of the capital," UN Special Representative Volker Perthes told the Security Council Tuesday.
Perthes said he maintained contact with both generals currently at war: army chief Abdel Fattah al-Burhan and his deputy-turned-rival, Mohamed Hamdan Daglo, who commands the heavily-armed paramilitary Rapid Support Forces (RSF).
"There is yet no unequivocal sign that either is ready to seriously negotiate," Perthes said.
Security fears were compounded when the World Health Organization (WHO) warned of a "huge biological risk" after fighters occupied a Khartoum laboratory holding samples of cholera, measles, polio and other infectious diseases.
With the heaviest combat eased, thousands of foreigners as well as Sudanese continued to flee the capital.
Ten days of heavy fighting until Monday has killed hundreds of people, left bodies rotting in the streets, and some neighbourhoods of greater Khartoum in ruins.
Bewildered civilians were seen walking down one street in Khartoum North where almost all buildings were blasted out and smoke rose from scorched ruins, in unverified video posted on social media.
Witnesses in the same area later reported air strikes, and paramilitary forces firing anti-aircraft weapons.
In the capital's twin city Omdurman, witnesses heard gunfire.
Late Tuesday witnesses reported more air strikes in Khartoum North where they said fighter jets struck RSF vehicles heading north.
The RSF posted a video in which it claimed to be in control of an oil refinery and the associated Garri power plant more than 70 kilometres (43 miles) north of Khartoum.
Shortly before, the army had warned in a Facebook post of "heavy movement towards the refinery in order to take advantage of the truce by taking control of the refinery".
The two sides have both made unverifiable claims to control of key sites, adding to what experts call an overwhelming state of fear in the capital.
According to lawyers, at least one jailbreak took place earlier this week, with reports of another at Kober prison, where former dictator Omar al-Bashir -- who is wanted by the International Criminal Court for war crimes, crimes against humanity and genocide -- is being held.
Detained regime official and former top aide of Bashir, Ahmed Harun -- who is also wanted by the ICC for genocide and crimes against humanity -- said in a recorded address to Sudanese television late on Tuesday that a number of officials from Bashir's regime were out of jail.
"We remained in our detention at Kober, under the crossfire of this current battle, for nine days," even after the jail was emptied of both guards and prisoners, and "have now taken responsibility for our protection in our own hands", in another location.
With much of the city of five million seeing a relative reduction in fighting, foreign governments have been organising road convoys, aircraft and ships to get thousands of their nationals out.
"The most difficult thing was the sounds of the bombing and the jet fighters while flying above our home. That horrified the children," said Safa Abu Taher, who landed with her family at a military airport in Jordan Tuesday night.
Witnesses in Wad Banda, West Kordofan state, reported clashes between the army and RSF, including the use of fighter jets.
West Kordofan is adjacent to Sudan's Darfur region which has seen heavy fighting and the looting of aid depots, but the UN cited reports that in North Darfur state a local ceasefire had been in place since late last week.
In West Darfur, "near the Chadian border, fighting has resumed with increased and worrying reports of tribes arming themselves and joining the fight," Perthes said Tuesday, adding that "intercommunal clashes" have also broken out in Blue Nile, on the southeastern border with Ethiopia.
'Tens of thousands' fleeing
A UN report said "shortages of food, water, medicines and fuel are becoming extremely acute, especially in Khartoum and surrounding areas".
"In some places, humanitarian aid is all that is keeping famine at bay," UN chief Antonio Guterres said Tuesday.
Despite the rocketing prices of fuel and bus tickets required to escape, the UN "received reports of tens of thousands of people arriving in the Central African Republic, Chad, Egypt, Ethiopia, and South Sudan," Assistant Secretary General Joyce Msuya said Tuesday.
The UN warned it was bracing for an exodus of up to 270,000 refugees to Sudan's even poorer neighbours Chad and South Sudan.
Fighting has killed at least 459 people and wounded more than 4,000 across Africa's third-biggest country, according to UN agencies.
The UN warned Tuesday that an estimated 219,000 women in Khartoum are pregnant, with "24,000 expected to give birth in the coming weeks", amid a near-absence of medical care.
In an additional threat, the WHO's representative in Sudan, Nima Saeed Abid, said there was "a huge biological risk associated with the occupation of the central public health lab... by one of the fighting parties".
Sudan, one of the world's poorest nations, has a troubled history of military coups.
The RSF emerged from the Janjaweed militia that then-president Omar al-Bashir unleashed in the Darfur region two decades ago, leading to war crimes charges against Bashir and others.
The military toppled Bashir in April 2019 following mass citizen protests that raised hopes for a transition to democracy.
The two generals seized power in the 2021 coup, but later fell out, most recently over the planned integration of the RSF into the regular army.
