CAIRO (AP) — Fighters from a paramilitary force and their allied Arab militias rampaged through a town in Sudan’s war-ravaged region of Darfur, reportedly killing more than 800 people in a multiday attack, doctors and the U.N. said.

The attack on Ardamata in West Darfur province earlier this month was the latest in a series of atrocities in Darfur that marked the monthslong war between the Sudanese military and the paramilitary Rapid Support Forces, RSF.

Sudan has been engulfed in chaos since in mid-April, when simmering tensions between military chief Gen. Abdel-Fattah Burhan and the commander of the paramilitary Rapid Support Forces, Gen. Mohamed Hamdan Dagalo, exploded into open warfare.

The war came 18 months after both generals removed a transitional government in a military coup. The military takeover ended Sudan’s short-lived fragile transition to democracy following a popular uprising that forced the overthrow of longtime strongman Omar al-Bashir in April 2019.

In recent weeks the RSF advanced in Darfur, taking over entire cities and towns across the sprawling region, despite the warring parties’ return to the negotiating table in Saudi Arabia late last month. The first round of talks, brokered by the U.S. and Saudi Arabia, failed to establish a cease-fire.

The dayslong attack in Ardamata came after the RSF took over a military base in the town after a brief fighting on Nov. 4 with troops there, said Salah Tour, head of the Sudanese Doctor’s Union in West Darfur. He said the military withdrew from the base, adding that around two dozen wounded troops fled to Chad.

Spokespeople for the military and the RSF didn’t respond to phone calls seeking comment.

After seizing the military base, the RSF and their allied Arab militias rampaged through the town, killing non-Arabs inside their homes and torching shelters housing displaced people, Tour said.

“They violently attacked the town,” he said, adding that the RSF and their militias targeted the African Masalit tribe. “They went from house to house, killing and detaining people.”

The Darfur Bar Association, an advocacy group, accused RSF fighters of committing “all types of serious violations against defenseless civilians” in Ardamata. It cited an attack on Nov. 6 during which the RSF killed more than 50 people including a tribal leader and his family.

The UNHCR said more than 800 people have been reportedly killed and 8,000 others fled to neighboring Chad. The agency, however, said the number of people who fled was likely to be an underestimate due to challenges registering new arrivals to Chad.

The agency said about 100 shelters in the town were razed to the ground and extensive looting has taken place there, including humanitarian aid belonging to the agency.

“Twenty years ago, the world was shocked by the terrible atrocities and human rights violations in Darfur. We fear a similar dynamic might be developing,” said U.N. High Commissioner for Refugees, Filippo Grandi.

The U.S. State Department said it was “deeply disturbed by eyewitness reports of serious human rights abuses by the RSF and affiliated militias, including killings in Ardamata and ethnic targeting of the Masalit community leaders and members.

“These horrifying actions once again highlight the RSF’s pattern of abuses in connection with their military offensives,” it said in a statement.

Ardamata is located a few kilometers (miles) north of Geneina, the provincial capital of West Darfur. The RSF and Arab militias launched attacks on Geneina, including a major assault in June that drove more of its non-Arab populations into Chad and other areas in Sudan.

The paramilitary group and its allied Arab militias were also accused by the U.N. and international rights groups of atrocities in Darfur, which was the scene of a genocidal campaign in the early 2000s. Such atrocities included rape and gang rape in Darfur, but also in the capital, Khartoum. Almost all reported cases were blamed on the RSF.

The U.N. Human Rights Office said in July a mass grave was found outside Geneina with at least 87 bodies, citing credible information. Such atrocities prompted the International Criminal Court’s prosecutor to declare that he was investigating alleged war crimes and crimes against humanity in the latest fighting in Darfur.

The conflict killed about 9,000 people and created “one of the worst humanitarian nightmares in recent history,” according to the U.N. Undersecretary-General Martin Griffiths. More than 6 million people were also forced out of their homes, including 1.2 million who have sought refuge in neighboring countries, according to the U.N. figures.

The fighting initially centered in Sudan’s capital, Khartoum, but quickly spread to other areas across the east African nation, including Darfur.

It turned the capital into a battle ground, wrecking most of civilian infrastructure, most recently the collapse of a bridge over the Nile River connecting Khartoum’s northern part with the capital’s sister city of Omdurman. Both sides traded accusations of having exploded the Shambat bridge.