CAIRO (AP) — Heavy artillery fire killed at least 11 people and wounded 90 in a major city in conflict-torn Sudan, the aid group Doctors Without Borders said.

The attack took place on Thursday in the Karari neighborhood in the city of Omdurman, just next to the Sudanese capital of Khartoum, the group said, without saying which of the country’s warring parties was responsible.

The group, also known by its French acronym MSF, said on X, formerly known as Twitter, that children were among those killed and that the wounded are being treated at Al Nao hospital in Omdurman. The hospital is one of several facilities where the medical group operates.

Sudan has been rocked by violence since mid-April, when fighting erupted between the country’s military, led by Gen. Abdel Fattah Burhan, and the paramilitary Rapid Support Forces, commanded by Gen. Mohamed Hamden Dagalo.

The clashes then spread to several parts of the country, reducing Khartoum and Omdurman to an urban battlefield, and fueling ethnic violence in the restive western Darfur region.

The military and the paramilitary force did not respond to requests for comment.

Separately, MSF said one of its vans was hit by gunfire Thursday while traveling between Khartoum and Wadi Madani, a small city roughly 100 kilometers (60 miles) east of Khartoum. No one was hurt in the incident. On Friday, the MSF blamed the military for the attack.

Wadi Madani is entirely controlled by the army, while Khartoum remains contested, with the paramilitary occupying vast swaths of the city.

“In September, our teams have already responded to seven mass casualty incidents in hospitals we support. The suffering this brutal fighting is causing for the population is unbearable,” MSF posted on X.

The fighting has driven 5.5 million people from their homes, according to the latest United Nations' figures. There are 4.3 million people internally displaced within Sudan while 1.2 million have crossed into neighboring countries.

Clementine Nkweta-Salami, the U.N.'s humanitarian coordinator in Sudan, said Thursday that 18 million people are in need of humanitarian assistance. So far, aid agencies have only reached around 3.6 million people in the country, she said.

“The population of Sudan is balancing on a knife’s edge,” she added, describing the situation as “the world's fastest growing displacement crisis.”

Sudan's conflict has killed at least 5,000 and wounded more than 12,000, according to the U.N. Activists and medical groups in Sudan say the true death is far higher.