Around 70 people were killed in an attack on the only functional hospital in the besieged city of El Fasher in Sudan, the chief of the World Health Organization said Sunday, part of a series of attacks coming as the African nation's civil war escalated in recent days.

The attack on the Saudi Teaching Maternal Hospital, which local officials blamed on the rebel Rapid Support Forces, came as the group was experiencing apparent battlefield losses to the Sudanese military and allied forces under the command of army chief Gen. Abdel-Fattah Burhan. That includes Burhan appearing near a burning oil refinery north of Khartoum on Saturday that his forces said they seized from the RSF.

Saudi Arabia’s Foreign Ministry denounced the attack as “a violation of international law.”

International mediation attempts and pressure tactics, including a U.S. assessment that the RSF and its proxies are committing genocide, and sanctions targeting Burhan, haven't halted the fighting.

Reported attack follows RSF warning

WHO Director-General Tedros Adhanom Ghebreyesus posted the death toll in the hospital attack in El Fasher on the social platform X.

Officials and others in the capital of North Darfur province had cited a similar figure Saturday, but Tedros is the first international source to provide a casualty number. Reporting on Sudan is incredibly difficult given communication challenges, the indiscriminate violence faced by civilians and exaggerations by both the RSF and the Sudanese military.

“The appalling attack on Saudi Hospital in El Fasher, Sudan, led to 19 injuries and 70 deaths among patients and companions,” Tedros wrote. “At the time of the attack, the hospital was packed with patients receiving care.”

Another health facility in Al Malha also was attacked Saturday, he added.

“We continue to call for a cessation of all attacks on health care in Sudan, and to allow full access for the swift restoration of the facilities that have been damaged,” Tedros said. “Above all, Sudan’s people need peace. The best medicine is peace.”

Read: Sudan's warring forces are escalating attacks and outsiders are 'fueling the fire,' Guterres says

Tedros didn't identify who launched the attack, though local officials had blamed the RSF for the assault. Sudan’s Foreign Ministry also accused the RSF of launching a drone attack targeting the hospital’s emergency ward, describing the assault as a “massacre.”

U.N. official Clementine Nkweta-Salami, who coordinates humanitarian efforts for the world body in Sudan, warned Thursday that the RSF earlier had given “a 48-hour ultimatum to forces allied to the Sudanese Armed Forces to vacate the city and indicated a forthcoming offensive.”

“Since May 2024, El Fasher has been under RSF siege,” she said. “Civilians in El Fasher have already endured months of suffering, violence and gross human rights abuses under the prolonged siege. Their lives now hang in the balance due to an increasingly precarious situation.”

In a statement on Sunday night, the RSF alleged that the Sudanese military and its allies attacked the hospital in El Fasher, but offered no evidence to support the claim.

El Fasher is more than 800 kilometers (500 miles) southwest of Khartoum. The city is now estimated to be home to more than 1 million people, many of whom have been displaced by the war.

The U.N. said in December that the RSF siege had killed 782 civilians and wounded more than 1,140 others, warning that the figures likely were higher.

The Saudi hospital, just north of El Fasher's airport, sits near the front lines of the war and has been repeatedly hit by shelling. Still, its doctors continue surgeries, sometimes by the light of cellphones while the hospital is hit.

However, the RSF appeared in recent days to have lost control of the Khartoum refinery, the biggest in Sudan and crucial to both its economy and that of South Sudan. Burhan's forces also say they broke another RSF besiegement of the Signal Corps headquarters in northern Khartoum. The rebels claimed they were “tightening the noose” around that base.

Sudan’s war sees brutality by fighters

Read more: Paramilitary rampage kills over 120 in east-central Sudan: UN

Sudan has been unstable since a popular uprising forced the removal of longtime dictator Omar al-Bashir in 2019. A short-lived transition to democracy was derailed when Burhan and Gen. Mohammed Hamdan Dagalo of the RSF joined forces to lead a military coup in October 2021.

Al-Bashir faces charges at the International Criminal Court over carrying out a genocidal campaign in the early 2000s in the western Darfur region with the Janjaweed, the precursor to the RSF. Rights groups and the U.N. say the RSF and allied Arab militias are again attacking ethnic African groups in this war.

The RSF and Sudan’s military began fighting each other in April 2023. Their conflict has killed more than 28,000 people, forced millions to flee their homes and left some families eating grass in a desperate attempt to survive as famine sweeps parts of the country.

Other estimates suggest a far higher death toll in the civil war.

On Sunday, Burhan traveled to the military's General Command headquarters in Khartoum, a building he hadn't been to since the fighting broke out in 2023. The headquarters is near Khartoum International Airport, which has seen fierce fighting during the war.

“The armed forces are in their best condition and we will move forward with the determination of our people to eliminate the rebellion in all of Sudan,” Burhan said, according to the state-run SUNA news agency.