Kabul, Afghanistan (CNN)Aerial bombardments hit a Doctors Without Borders hospital in the battleground Afghan city of Kunduz early Saturday, killing at least 16 people, including nine staffers and seven patients, the charity said. Three of those patients were children. The circumstances weren't immediately clear, but the U.S. military conducted an airstrike in Kunduz at the time, and the incident is being investigated, U.S. Army Col. Brian Tibus said.
Specifically, the military is investigating whether a U.S. AC-130 gunship -- which was in the area firing on Taliban positions to defend U.S. special operations troops there -- is responsible, a U.S. military official said on condition of anonymity.
The attacks, which injured at least 37 other people and left part of the hospital in flames and rubble, came on roughly the sixth day of fighting between Afghan government forces -- supported by U.S. airpower and military advisers -- and the Taliban, which invaded the city early this week.
The global charity expressed shock, saying it had told all warring parties the exact location of the trauma center, including most recently on Tuesday.
The charity, which had said the facility had been caring for hundreds already hurt in days of fighting, also said that it had alerted U.S. and Afghan military officials of Saturday's attack, but that the attacks continued.
"The bombing continued for more than 30 minutes after American and Afghan military officials in Kabul and Washington were first informed," the charity, known internationally as Medecins Sans Frontieres, said. "MSF urgently seeks clarity on exactly what took place and how this terrible event could have happened."
Thirty people were unaccounted for, MSF said, and it expects the number of people killed or injured to go up.
When the aerial attack occurred, 105 patients and their caretakers were in the hospital. More than 80 MSF international and national staff were present.
The U.S. special operations troops were in the area advising Afghan forces, the military official speaking anonymously said. The official stressed that the information about the probe was preliminary, and that a thorough investigation was underway.
Pribus said a "manned, fixed-wing aircraft" conducted a strike "against individuals threatening the force" at 2:15 a.m., and that the strike "may have resulted in collateral damage to a nearby medical facility."
The AC-130 is a large, fixed-wing gunship built on a C-130 Hercules cargo plane airframe, according to Boeing, the manufacturer. The AC-130U, the most advanced model, is armed with a 25-millimeter Gatling gun, a 40-mm cannon and a 105-mm cannon, according to the Boeing website.
