UPDATE: 4:52 p.m. EDT: The death toll in a likely U.S. airstrike on a Doctors Without Borders hospital in Kunduz, Afghanistan, has risen to 22 people, from the original 19 estimated, Reuters reported, prompting the nonprofit organization to call for an independent investigation of the attack that struck Saturday evening.

"Under the clear presumption that a war crime has been committed, [Doctors Without Borders] demands that a full and transparent investigation into the event be conducted by an independent international body," read a statement published by the organization on their website Sunday. The accusation that a "war crime has been committed" came as U.S. defense officials pledged to look into U.S. involvement in the airstrike.

Original Story:

After apparent U.S.-led airstrikes in Afghanistan devastated a hospital run by the international humanitarian organization Doctors Without Borders and killed at least 19 people Saturday, Afghan Defense Ministry officials alleged Taliban militants had been using the hospital as the equivalent of a human shield and directly firing on American and Afghan armed forces. These forces have been attempting to retake the city of Kunduz from the Taliban during the past week, amid escalating violence in the northern region of the country.

Doctors Without Borders categorically denied the allegation in a statement cited by Reuters Sunday.

The airstrikes greatly damaged the hospital, which featured the only intensive-care unit (ICU) in the region. Even though hospital officials had informed both U.S. and Afghan forces of their location, the shelling continued for more than 30 minutes. The entire ICU burned to the ground with patients inside, in an attack that the United Nations has condemned as potentially criminal.

The acting governor of the Kunduz province called the Doctors Without Borders hospital a “Taliban base.” Hamdullah Danishi said in an interview with the Washington Post that “the hospital campus was 100 percent used by the Taliban.”

Doctors Without Borders vehemently denied the allegation. “The gates of the hospital compound were closed all night so no one that is not staff, a patient or a caretaker was inside the hospital when the bombing happened,” the group said in its statement. “In any case, bombing a fully functioning hospital can never be justified.” The organization has now pulled out of the region.

Afghan forces Afghan military personnel stand guard at the airport in Kunduz during fighting between Afghan security forces and Taliban militants Oct. 1, 2015. Photo: AFP/Getty Images

The struggle to retake Kunduz has highlighted the potential inability of U.S.- and NATO-trained Afghan forces to keep the situation stable in the restive region. In Kunduz, several thousand Afghan military personnel were unable to keep several hundred Taliban fighters from taking control of the city.

The U.S. has spent billions of dollars training foreign fighters, and many defense officials with experience on the ground have observed the inability of these fighters to maintain security after American troops have pulled out. “Our track record at building security forces over the past 15 years is miserable,” Karl Eikenberry, a former military commander and U.S. ambassador to Afghanistan, told the New York Times.