At least 56 civilians have been killed in cities and regions around the country, the Sudanese Doctors’ Union have said.
It added that 595 people, including combatants, had been wounded since the fighting erupted on Saturday with dozens of military personnel dead, and some still being treated in hospitals.
Reuters reports heavy artillery firing across Khartoum, Omdurman and nearby Bahri were heard by eyewitnesses in the early hours of Sunday morning, and there was also gunfire heard in the Red Sea city of Port Sudan.
The Union had earlier said it recorded deaths at Khartoum’s airport and Omdurman, as well as west of Khartoum in the cities of Nyala, El Obeid and El Fasher.
The Rapid Support Forces (RSF), on Saturday claimed to have seized the presidential palace, army chief’s residence, state television station and airports in Khartoum, the northern city of Merowe, El Fasher and West Darfur state.
However, the army rejected those assertions.
The Sudanese air force told people to stay indoors while it conducted what it called an aerial survey of RSF activity, while a holiday was declared in Khartoum state for Sunday, closing schools, banks and government offices.
Gunfire and explosions could be heard across the capital, where TV footage showed smoke rising from several districts and social media videos captured military jets flying low over the city, at least one appearing to fire a missile.
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.
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”.
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.
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