A U.S.-led bombing accidentally hit a Doctors Without Borders hospital in Kunduz, Afghanistan, resulting in the death of 23 civilians.

The victims included 13 staff members and 10 patients. Three of the patients who were killed were children. Doctors Without Borders also reported that 37 people were wounded. One nurse recounted the terrible situation to the Huffington Post.

“There are no words for how terrible it was. In the intensive care unit, six patients were burning in their beds,” Lajos Zoltan Jecs said in an account posted on the MSF website.

She continued describing the situation. She watched colleagues die, heard patients calling out for help in all directions, and watched some of the staff just freeze, tears streaming down their faces.

General John Campbell addressed reporters at the Pentagon Monday. He stated that the strikes were called for by Afghan forces to protect U.S. forces.

“We have now learned that on October 3, Afghan forces advised that they were taking fire from enemy positions and asked for air support from U.S. forces,” he said. “An airstrike was then called to eliminate the Taliban threat, and several innocent civilians were accidentally struck.” Campbell also offered his condolences.

Afghan officials called the situation a tragedy, but have remained mute on the situation.

U.S., NATO, and Afghan officials are investigating the situation. Doctors Without Borders, also known as Medecins Sans Frontieres (MSF), is demanding an independent investigation and calling the situation a “war crime.”

“Under the clear presumption that a war crime has been committed, MSF demands that a full and transparent investigation into the event be conducted by an independent international body,” the organization said. “Relying only on an internal investigation by a party to the conflict would be wholly insufficient.”

MSF reports that the series of bombings took place in 15 minute intervals between 2:08 a.m. and 3:15 a.m. Saturday. The charity added that the bombings continued even after U.S. and Afghan officials were notified that the hospital was being attacked.

Afghan police report that Taliban militants had been using the hospital compound as a hiding place, but Doctors Without Borders denied the claims.

The charity has since closed the hospital due the extensive damages to the building and equipment. In less than a week, MSF has treated 394 wounded people in Kunduz.

“There is no access to trauma care now for the civilians and for the wounded in the whole area of Kunduz, which is some kind of battleground for the moment,” said Christopher Stokes, the aid group’s general director.