Fierce clashes have been reported across Sudan as fighting between rival armed factions continues to spread.

Violence between the army and a paramilitary group called the Rapid Support Forces (RSF) continued overnight into its third day.

Nearly 100 people have been killed, a doctors' union said, and one estimate put the number of injured at 1,100.

Both sides claimed to control key sites in the capital Khartoum, where residents sheltered from explosions.

Earlier on Sunday, they held a temporary ceasefire to allow the wounded to be evacuated, although it was not clear how strictly they stuck to it.

Doctors warned that the situation at hospitals in Khartoum is extremely difficult, and that the fighting was stopping both staff and medical supplies from reaching injured people.

The fighting is part of a vicious power struggle within the country's military leadership, which has escalated into violence between rival factions.

The two men at its centre disagree over how the country should transition to civilian rule. Sudan has been run by generals since a coup overthrew the long-standing authoritarian president, Omar al-Bashir, in 2019.

On Sunday and early Monday, the RSF claimed to occupy sites in the capital Khartoum such as the presidential palace, and the adjoining city of Omdurman, as well as in the western region of Darfur and Merowe Airport in the north of the country.

But some accounts indicated that the army had regained control of the airport, with the military saying they were dealing with "small pockets of rebels".

The army has previously denied that the RSF had seized key sites in the capital, and witnesses in the country told Reuters news agency that the army appeared to be making gains after blasting RSF bases with air strikes.

Residents of Khartoum have spoken of fear and panic, and reported gunfire and explosions.

"We're scared, we haven't slept for 24 hours because of the noise and the house shaking," Huda, a Khartoum resident, told the Reuters news agency. "We're worried about running out of water and food, and medicine for my diabetic father."

Another Khartoum resident, Kholood Khair, told the BBC that residents could not be sure of safety anywhere. "All civilians have been urged to stay at home, but that has not kept everyone safe."

The fighting is between army units loyal to the de facto leader, Gen Abdel Fattah al-Burhan, and the RSF, a notorious paramilitary force commanded by Sudan's deputy leader, Mohamed Hamdan Dagalo, better known as Hemedti.

The major sticking points are over the plans to incorporate the 100,000-strong RSF into the army, and over who would then lead the new force.

The brief pause in the fighting on Sunday followed complaints from doctors' unions that it was difficult for medics and sick people to get to and from hospitals while the fighting was raging.

A chorus of international voices has called for a permanent end to the violence.

Leading Arab states and the US have also urged a resumption of talks aimed at restoring a civilian government, while the African Union has announced that it is sending its top diplomat, Moussa Faki Mahamat, to try to negotiate a ceasefire.

Egypt and South Sudan also offered to mediate between the warring factions, according to a statement by the Egyptian presidency.

Death toll estimates have varied.

The Central Committee of Sudan Doctors reported 97 civilians killed and dozens among security forces dead, as well as 942 people injured.

Meanwhile, the World Health Organisation says more than 83 people have been killed and more than 1,100 people injured across the country since Thursday, when the RSF began mobilising its forces. It does not specify how many civilians have died in the fighting.

Among the dead are three staff members of the UN World Food Programme (WFP), which has suspended its operations in the country.

In a statement, the WFP said it was "horrified" by the news of the deaths, adding that one of its aircraft had been damaged at Khartoum International Airport during an exchange of gunfire on Saturday, which it says impacted its ability to provide aid.

Sudan state television is reported to have stopped transmissions, but it was not immediately clear what caused the break in programming.