Three Doctors Without Borders staff killed in bombing of hospital in Kunduz, as NATO admits it may have been involved.

Surviving MSF staff were in shock after the clinic in Kunduz sustained heavy damage in the bombardment [MSF/Al Jazeera]

Doctors Without Borders (MSF) says three of its staff have been killed in an overnight bombing of a hospital in the embattled Afghan city of Kunduz.

NATO said on Friday that a US air strike “may have” hit the hospital, which is run by the medical charity, adding that the attack may have resulted in collateral damage.

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 (20:40 GMT) local time … the MSF trauma centre in Kunduz was hit several times during sustained bombing and was very badly damaged,” MSF said in a statement on Friday.

Deeply shocked at bombing of MSF hospital in #Kunduz. Staff and patients killed. MSF urges fighting parties to respect health facilities

— MSF International (@MSF) October 3, 2015

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 air strike in Kunduz at 2:15am 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.

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”.

The MSF trauma centre in Kunduz is the only medical facility in the region that can deal with major injuries.

Al Jazeera’s Qais Azimy, reporting from Puli Khumri, about 130km from Kunduz, said the bombing injured at least 50 people.

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, our correspondent said.

Kunduz is facing a humanitarian crisis, with thousands of civilians caught in the crossfire between government forces and Taliban fighters.

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 neighbouring 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 air strikes, have been going from house to house in Kunduz in a bid to flush Taliban fighters out of the city.

The Taliban’s offensive in Kunduz, their biggest tactical success since 2001, marks a major blow for Afghanistan’s Western-trained forces, who have largely been fighting on their own since last December.

Civilian and military casualties caused by NATO forces have been one of the most contentious issues in the 14-year campaign against the Taliban, provoking harsh public and government criticism.

US-led NATO forces ended their combat mission in Afghanistan last December, though a 13,000-strong residual force remains for training and counterterrorism operations.

But there has been an escalation in air strikes by NATO forces in recent months despite the drawdown.

MSF’s hospital is the only facility of its kind in the whole north-eastern region of Afghanistan [MSF]

The medical charity urges all parties to the violence to respect the safety of health facilities, patients and staff [MSF]