CAIRO (AP) — The notorious Rapid Support Forces paramilitary group, fighting Sudan’s military for over a year, fired shots and looted a health facility in the western region of Darfur, forcing its closure, an international aid group said.

The RSF, attacked the South Hospital in al-Fasher, the capital city of North Darfur province on Sunday, opening fire on medical staff and patients, Doctors Without Borders said in a statement.

This came as the RSF intensified its offensive to try and wrest control of the city, the military’s last stronghold in the sprawling Darfur region. Two weeks of fighting last month in and around al-Fasher has killed more than 120 people.

Meanwhile, the military has allied itself with rebel groups and formed a joint force to retain control of the city, where hundreds of thousands of displaced people have taken shelter since the conflict began.

“It is outrageous that the RSF opened fire inside the hospital. This is not an isolated incident, as staff and patients have endured attacks on the facility for weeks from all sides, but opening fire inside a hospital crosses a line,” said Michel Lacharite, head of emergency operations at Doctors Without Borders.

At the time of the attack, there were 10 patients and a reduced medical crew as the aid group and the Sudanese health ministry had begun evacuating patients and transferring medical services last week to other facilities, the aid group said.

Most patients and the medical team, including Doctors Without Borders staff, managed to flee the shooting. It was not immediately clear whether there were casualties from the attack, according to the aid group.

A spokesman for the RSF didn’t return phone calls seeking comment.

The facility had been hit by mortar shells and bullets three times between May 25 and June 3, killing two people and wounding 14 patients, Doctors Without Borders said.

Sudan’s conflict began in April last year when soaring tensions between the leaders of the military and the RSF exploded into open fighting in the capital, Khartoum and elsewhere in the country.

The war has wrecked Sudan, killing more than 14,000 people and wounding thousands others, while pushing its population to the brink of famine. The U.N. food agency warned the warring parties last month that there is a serious risk of widespread starvation and death in Darfur and elsewhere in Sudan if they don’t allow humanitarian aid into the vast western region.

Widespread sexual violence and other atrocities from both sides have also been reported, amounting to war crimes and crimes against humanity, according to the United Nations.

Two decades ago, the RSF was born out of Arab militias, commonly known as Janjaweed, mobilized by former Sudanese President Omar al-Bashir against populations that identify as Central or East African in Darfur. At the time, they were accused of mass killings, rapes and other atrocities, and Darfur became synonymous with genocide.

Janjaweed groups still aid the RSF.