Doctors Without Borders (MSF) says at least nine of its staff have been killed in an overnight bombing of a hospital in the embattled Afghan city of Kunduz.
Another 37 people were wounded in the attack, including 19 MSF staff, the medical charity organization said.
NATO said on Friday that a US airstrike "may have" hit the hospital, which is run by the medical charity, adding that the attack may have resulted in collateral damage, Al Jazeera reported.
An MSF spokesperson said that the death toll is likely to rise, as the "fluid situation at the clinic hampered information gathering.
"The bombing struck the dormitories of the hospital, which explains why we have only seen deaths among our staff and not among patients," MSF spokesperson Dalila Mahdawi said.
The MSF hospital is seen as a key medical lifeline in the region, which has been running "beyond capacity" in recent days of fighting which saw the Taliban seize control of the provincial capital for several days.
"At 2:10 am (2040 GMT) local time ... the MSF trauma center in Kunduz was hit several times during sustained bombing and was very badly damaged," MSF said in a statement on Friday.
At the time of the bombing, 105 patients and their caretakers and more than 80 MSF international and national staff were present in the hospital, the charity said.
- NATO Investigation
NATO said in a statement that US forces conducted an airstrike in Kunduz at 2:15 am local time "against individuals threatening the force".
"The strike may have resulted in collateral damage to a nearby medical facility. This incident is under investigation," the statement said.
MSF said it gave the coordinates of the hospital to Afghan and US forces several times to avoid being caught in crossfire.
"Precise location of our Kunduz hospital communicated to all parties on multiple occasions over past months," as well as earlier this week, the group said on Twitter.
In a statement, the Taliban accused "barbaric American forces" of deliberately carrying out Saturday's strike, which "killed and wounded tens of doctors, nurses and patients".
Following the attack, the medical charity urged all parties involved in the violence to respect the safety of health facilities, patients and staff.
- Battle for Kunduz
The development came a day after the Afghan government claimed it had successfully retaken parts of Kunduz from Taliban fighters who had controlled the strategic city since Monday.
The Taliban, however, claimed it remained in control of most of Kunduz.
Precise losses in the fighting were not known, but health authorities said on Friday that at least 60 people have been killed and 400 wounded.
As fighting spreads in neighboring Badakhshan, Takhar and Baghlan provinces, concerns are mounting that the seizure of Kunduz was merely the opening gambit in a new, bolder Taliban strategy to tighten the grip across northern Afghanistan.
Afghan forces, backed by NATO special forces and US airstrikes, have been going from house to house in Kunduz in a bid to flush Taliban fighters out of the city.
Reporters said heavy fighting was ongoing in the center of Kunduz.
"Sources inside the city are reporting heavy clashes between the Taliban and the Afghan Army. There is no set frontline between the two sides so the fighting is from street to street at the moment.
"People inside the city are suffering. There is a shortage of food, water and electricity," our correspondent said.
