At least two people were killed when Sudan's paramilitary Rapid Support Forces attacked a major camp for displaced people in the North Darfur region, activists said on Monday.
The Zamzam camp, south of the regional capital El-Fasher, was hit by heavy RSF rocket and artillery fire on Sunday, said the local resistance committee in El-Fasher.
The "indiscriminate" attack killed at least two people and wounded a dozen, said the committee, one of hundreds of volunteer groups coordinating aid in Sudan.
Medical charity Doctors without Borders (MSF) said Monday its teams received eight injured people a day earlier, including women and children as young as four with "severe injuries such as chest trauma and fractures".
It said four critically injured patients were transferred to another facility on Monday morning, just before renewed shelling hit areas near a market and the MSF's field hospital in the camp.
The MSF hospital was evacuated, with the last three intensive care patients -- dependent on oxygen -- being transferred.
"The situation is beyond chaotic: patients and medical staff are leaving the camp and trying to run for their lives," MSF said on X.
Sudan has been gripped since April last year by a war between the regular army and RSF that has killed tens of thousands of people and displaced more than 11 million.
Both sides face accusations of war crimes, including targeting civilians, shelling residential areas, and blocking or looting aid.
In recent weeks, the RSF has tightened its grip on El-Fasher, launching attacks on multiple fronts against Sudan's military and allied armed groups.
At least twice last year, in central and west Darfur, the RSF has used the proximity of refugee camps to army bases "as cover to conduct mass atrocities including mass killings", according to a report by Yale University's Humanitarian Research Lab.
Zamzam refugee camp is home to at least half a million people, according to the United Nations.
Satellite imagery verified by Yale University's research lab has shown "a significant increase" in displaced peoples flocking to the camp as well as the "creation of defensive positions" inside the camp in anticipation of expected RSF attacks.
UN humanitarian chief Tom Fletcher, after visiting Sudan and neighbouring Chad last week, called for immediate international action to address the crisis.
"It is a tough situation out there, the biggest humanitarian crisis in the world. And I've been talking to local people to host communities," Fletcher said in a weekend statement.
Nearly 26 million people -- about half the population -- face the threat of mass starvation in Sudan as both warring sides have been accused of using hunger as a weapon of war.
"These numbers are staggering, and we cannot turn our backs," Fletcher said.