A power struggle between Sudan's army and a notorious paramilitary force has rocked the country, with more than 50 civilians reported dead.

Residents dodged gunfire in the capital, Khartoum, as rival forces battled over the presidential palace, state TV, and army headquarters. 

Twenty-five people, including 17 civilians, have died in the city, a doctors' organisation said.

The clashes erupted after tensions over a proposed transition to civilian rule.

Both the army and its opponents, the Rapid Support Forces (RSF), claimed they had control of the airport and other key sites in Khartoum, where fighting continued overnight. 

Heavy artillery was heard in Omdurman, which adjoins Khartoum, and nearby Bahri in the early hours of Sunday morning. Eyewitnesses also reported gunfire in the Red Sea city of Port Sudan.

The army said jets were hitting RSF bases, and the country's air force told people to remain in their homes on Saturday night while it conducted a full aerial survey of paramilitary activity.

Residents of Khartoum told the BBC of their panic and fear, with one describing bullets being fired at the house next door.

At least 56 civilians have been killed in cities and regions around the country, a Sudanese doctors' committee said, adding that dozens of military personnel were dead, some of whom had been treated in hospitals.

In total, at least 595 people had been injured, it said.

Three employees for the World Food Programme (WFP), a UN body that delivers food assistance to vulnerable communities, were killed after the RSF and armed forces exchanged fire at a military base in Kabkabiya, in the west of the country.

Generals have been running Sudan since a coup in October 2021.

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

Hemedti said his troops would keep fighting until all army bases were captured. 

In response, Sudan's armed forces ruled out negotiations "until the dissolution of the paramilitary RSF".

'So much panic and fear'

In Khartoum, people were filmed running away and taking cover as black smoke rose over the city.

A Reuters journalist said there were armoured vehicles in the streets, while video showed a civilian plane ablaze at Khartoum airport. Saudi airline Saudia said one of its Airbuses came under fire.

Numerous airlines have suspended flights to Khartoum and neighbouring Chad has closed its border with Sudan.

"We don't have any electricity," a British-Sudanese doctor, who is visiting relatives in Khartoum, told the BBC. "It is hot. We can't afford to open the windows, the noise is deafening." 

Another eyewitness speaking to the BBC via her Kenya-based sister said: "Shooting is still ongoing and people are staying indoors - there is so much panic and fear."

Residents had not been expecting the clashes, she said, and many had been caught in transit, with bridges and roads closed and many schools in lockdown.

Duaa Tariq was speaking to the BBC when a military plane flew over her building. "They're shooting live ammunition at the roof of the house next door and we're just now taking shelter," she said.

The UK, the US, the EU, China and Russia have all called for an immediate end to the fighting. The UN's secretary general has spoken to Gen Burhan and Gen Dagalo, urging them to end the violence. 

US Ambassador John Godfrey said he "woke up to the deeply disturbing sounds of gunfire and fighting", and that he was "sheltering in place with the embassy team, as Sudanese throughout Khartoum and elsewhere are doing".

The RSF on Saturday claimed control of at least three airports, the army chief's residence and the presidential palace, but Gen Burhan denied this in an interview with al-Jazeera. 

There are also reports of clashes at the state TV station, which eyewitnesses say is now controlled by the RSF.

Earlier, the RSF had said that one of its camps in the south of Khartoum had been attacked. And on Saturday evening, Reuters reported that the army launched airstrikes on an RSF base in the north-west of the city, citing eyewitnesses. 

The army has said that RSF fighters have been attacking army camps and trying to seize the military headquarters.

"Clashes are ongoing and the army is carrying out its duty to safeguard the country," the AFP news agency quoted army spokesman Brig Gen Nabil Abdallah as saying. 

The Reuters news agency also cited witnesses as saying that there was gunfire in the northern city of Merowe. 

The RSF released a video that it said showed Egyptian troops who had "surrendered" to them in Merowe. The Egyptian military said its soldiers were in Sudan to conduct exercises with their Sudanese counterparts and that it was co-ordinating with Sudanese authorities to guarantee the safety of its personnel.

Generals run Sudan through the Sovereign Council. Gen Burhan is its president, while Hemedti is its vice-president.

A proposed move to a civilian-led government has foundered on the timetable to integrate the RSF into the army. The RSF wanted to delay it for 10 years, but the army said it should happen in two years.

Hemedti was a key figure in the conflict in Darfur that began in 2003 and has left hundreds of thousands dead.

Western powers and regional leaders had urged the two sides to de-escalate tensions and go back to talks aimed at restoring civilian rule. 

There had been signs on Friday that the situation would be resolved.

The 2021 coup ended a period of more than two years when military and civilian leaders were sharing power. That deal came after Sudan's long-term authoritarian President Omar al-Bashir was overthrown.

There have been regular pro-democracy protests in Khartoum since the coup.