Sudan's regular army and the paramilitary Rapid Support Forces (RSF) have been locked in a battle for power since April 2023 that has intensified this month with the army fighting to take back control of the capital.

RSF shelling killed 54 and injured 158 people at a busy market in army-controlled Omdurman, part of greater Khartoum, on Saturday, overwhelming the city's Al-Nao Hospital, according to a medical source and the health ministry.

"The shells hit in the middle of the vegetable market, that's why the victims and the wounded are so many," one survivor told AFP.

The RSF denied carrying out the attack.

Across the Nile in Khartoum proper, two civilians were killed and dozens wounded in an air strike on an RSF-controlled area, said the local Emergency Response Room, one of hundreds of volunteer groups coordinating emergency care across Sudan.

Although the RSF has used drones in attacks including on Saturday, the fighter jets of the regular armed forces maintain a monopoly on air strikes.

Both the RSF and the army have been repeatedly accused of targeting civilians and indiscriminately shelling residential areas.

- Metres away from hospital -

In addition to killing tens of thousands of people, the war has uprooted more than 12 million and decimated Sudan's fragile infrastructure, forcing most health facilities out of service.

A volunteer at Al-Nao Hospital told AFP it faced dire shortages of "shrouds, blood donors and stretchers to transport the wounded".

The hospital is one of the last medical facilities operating in Omdurman and has been repeatedly attacked.

According to the Sudanese doctors' union, one shell fell "just metres away from Al-Nao hospital" on Saturday.

The union said most of the victims were women and children, and called on nurses and doctors in the area to head to the hospital to relieve a "severe shortage of medical staff".

The fighting in the capital comes weeks after the army launched an offensive across central Sudan, reclaiming Al-Jazira state capital Wad Madani before setting its sights on Khartoum.

The RSF has since remained in control of the road between Wad Madani and Khartoum, but on Saturday an army-allied militia claimed control of the towns of Tamboul, Rufaa, Al-Hasaheisa, and Al-Hilaliya, some 125 kilometres (77 miles) southeast of the capital.

The group, the Sudan Shield Forces, is led by Abu Aqla Kaykal, who defected from the RSF last year and has been accused of atrocities against civilians both during his tenure with the RSF and now on the army's side.

Sudan remains effectively split, with the RSF in control of nearly all of the vast western region of Darfur and swathes of the south, and the army controlling the country's east and north.

After months of stalemate in greater Khartoum, the army has broken RSF sieges on several bases in the capital this month, including its headquarters, pushing the paramilitary increasingly into the city's outskirts.

Witnesses said Saturday's bombardment of Omdurman came from the city's western outskirts, where the RSF remains in control.

A resident of a southern neighbourhood reported rocket and artillery fire on the city's streets.

- Counter-offensive -

Saturday's bombardment came a day after RSF commander Mohamed Hamdan Daglo vowed to retake the capital from the army.

"We expelled them (from Khartoum) before, and we will expel them again," he told troops in a rare video address.

Greater Khartoum has been a key battleground in nearly 22 months of fighting between the army and the RSF, and has been reduced to a shell of its former self.

An investigation by the London School of Hygiene and Tropical Medicine found that 26,000 people were killed in the capital alone between April 2023 and June 2024.

Entire neighbourhoods have been taken over by fighters while at least 3.6 million civilians have fled, according to the United Nations.

Those unable or unwilling to leave have reported frequent artillery fire on residential areas, and widespread hunger in besieged neighbourhoods blockaded by opposing forces.

At least 106,000 people are estimated to be suffering from famine in Khartoum, according to the UN-backed Integrated Food Security Phase Classification, with a further 3.2 million experiencing crisis levels of hunger.

Nationwide, famine has been declared in five areas -- most of them in Darfur -- and is expected to take hold of five more by May.

Before leaving office, the administration of former US president Joe Biden sanctioned Sudan's army chief Abdel Fattah al-Burhan, accusing the army of attacking schools, markets and hospitals and using starvation as a weapon of war.

That designation came a week after Washington sanctioned the RSF commander for his role in "gross violations of human rights" in Darfur, where the State Department said his forces had "committed genocide" against non-Arab minority groups.