Witnesses report air strikes and paramilitary forces fire anti-aircraft weapons while WHO warns of "huge biological risk" after fighters occupy laboratory in capital Khartoum.

An evacuee receives sweets from a soldier of Saudi Royal Naval Forces as she arrives with others at Jeddah Port after being evacuated from Sudan.
An evacuee receives sweets from a soldier of Saudi Royal Naval Forces as she arrives with others at Jeddah Port after being evacuated from Sudan. (AP)

A US and Saudi Arabia-brokered ceasefire between Sudan's warring generals has 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.

Foreign nations stepped up efforts on Tuesday to evacuate their nationals from the chaos-torn African nation, but 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.

Fighting pits the army and its air support against heavily armed paramilitary Rapid Support Forces [RSF].

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 on Tuesday witnesses reported more air strikes in Khartoum North, where they said fighter jets struck RSF vehicles heading north.

Meanwhile, Sudanese ex-official Ahmed Haroun, who served under ex-president Omar al Bashir and is wanted by the International Criminal Court, said that he and other former officials of Bashir's government had left Kober prison and would take responsibility for their own protection.

The statement comes after reports that prisoners at Kober prison, which held ex-Sudanese president and other top deputies, had staged a break earlier this week.

It was not immediately clear if Bashir, who has spent extended periods in a military hospital, was at the prison.

READ MORE: Türkiye continuing evacuation efforts from Sudan: Cavusoglu

'Children horrified'

The ceasefire appears to be partially holding but there is no sign the warring parties are ready to seriously negotiate, the UN special envoy on Sudan said.

This suggested "that both think that securing a military victory over the other is possible," envoy Volker Perthes told the UN Security Council. 

"This is a miscalculation."

"It seems to be holding in some parts so far. However, we also hear continuing reports of fighting and movement of troops," said Perthes, who spoke via video from Port Sudan.

Meanwhile, the Rapid Support Forces or 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 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".

But with much of the city of five million seeing a relative reduction in fighting, witnesses said, foreign governments have been organising road convoys, aircraft and ships to get their nationals out since the weekend.

More than 6,400 people have fled Sudan in the evacuations including by sea to Saudi Arabia and by aircraft to Jordan and Djibouti.

"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 an Amman-area military airport on an evacuation flight Tuesday night.

Using buses, over 1,600 Turkish citizens were transported to Ethiopia from Sudan, Turkish diplomatic sources said.

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.

READ MORE: US: Sudan rivals agree to 72-hour ceasefire after hundreds killed

US 'deeply engaged'

A UN report said "shortages of food, water, medicines and fuel are becoming extremely acute, especially in Khartoum and surrounding areas".

Despite the rocketing prices of fuel and bus tickets required to escape, thousands of Sudanese have tried to flee to Egypt, and 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.

"Thankfully, we are safe," Omdurman resident Salwa Soliman told the AFP news agency at the Egyptian border.

"Neither the military nor the Rapid Support Forces [RSF] intercepted us" during a gruelling 1,000-kilometre journey, she said.

Fighting has killed at least 459 people and wounded more than 4,000 across Africa's third-biggest country, according to UN agencies.

Still, parts seem untouched. Khartoum residents fleeing to Wad Madani, 200 kilometres from the capital, were struck by the sight of normal life: stores open and not a gun in sight.

READ MORE: Clashes reported in Sudan despite RSF agreement on 72-hour Eid ceasefire

History of coups

The UN warned on 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 latest conflict is between forces loyal to army chief Abdel Fattah al Burhan against those of his former deputy Mohamed Hamdan Dagalo, who commands the RSF.

The RSF emerged from the Janjaweed militia that ex-president 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.

Calls for negotiations to end the crisis in Africa's third-largest nation have been ignored. For many Sudanese, the departure of diplomats, aid workers and other foreigners and the closure of embassies are terrifying signs that international powers expect the mayhem to only worsen.

READ MORE: Sudan 'on edge of abyss' after 10 days of brutal fighting: UN chief

Source: TRTWorld and agencies