At least 120 people are reported to have been killed in random shelling on Monday in the Dar-Salam area of the Sudanese city of Omdurman, across the Nile from the capital, Khartoum, according to a local volunteer network.

The Ombada Emergency Response Room said the death toll was provisional, suggesting that the number of victims could rise.

Rescuers say medical supplies are running low as health workers struggle to treat large numbers of people with injuries from bombardments.

Sudan's civil war, now 21 months old, has killed tens of thousands, uprooted over 12 million and pushed the country to the brink of famine, in what the UN describes as one of the world's worst humanitarian disasters.

It began last year after the leadership of the army and a paramilitary force, the Rapid Support Forces (RSF), fell out over the future direction of the country.

The Ombada Emergency Response Room did not specify who was behind the attack in Omdurman.

Volunteers and emergency response teams have faced challenges accessing certain areas because of ongoing fighting.

Most of Omdurman is under army control while the RSF holds the capital and part of the greater Khartoum area.

In the last past few weeks, the army has stepped up its offensive in Omdurman aiming to regain control. The army is reported to have seized three areas and confiscated weapons left behind by the paramilitary forces.

RSF fighters are pushing back from positions in two neighbourhoods. Residents on both sides of the Nile have reported shelling across the river, with bombs and shrapnel regularly striking homes and civilians.

"The area has been devastated by prolonged fighting exposing residents to stray bullets and shrapnel striking homes," the Ombada Emergency Response Room said.

Both sides have been accused of targeting civilians, including health workers, and indiscriminate shelling of residential areas.

The recent skirmishes have forced emergency response rooms, which support local communities amid the ongoing conflict, to shut several health centres affecting provision of medical services to thousands of residents.