KABUL - The US-led forces yesterday killed at least 19 people at a Kunduz hospital as the jets kept bombing the medical facility being run by a foreign aid group despite calls for halt to the airstrike.

The attack that also wounded three dozen people earned a strong reprimand from the UN, making the head of US-led international alliance to apologise and forcing the US Defence Department to order an inquiry though it said it was possibly a case of “collateral damage”.

But UN rights chief Zeid Ra’ad Al Hussein said the airstrike at the MSF-run hospital was “inexcusable” and “possibly criminal”. He called for a full and transparent investigation, noting that, “if established as deliberate in a court of law, an airstrike on a hospital may amount to a war crime.”

The strike came as the international forces are providing air support to the Afghan army to retake the northern city from the Taliban who raided and occupied the strategically important city six days ago, in the biggest victory of their near 14-year insurgency.

MSF (Medecins Sans Frontieres), also known as Doctors Without Borders, said more than half of the people who died in the night time attack were their staff.

Frantic MSF staff phoned military officials at Nato in Kabul and Washington after the attack, but bombs continued to rain down near the medical facility for nearly an hour, an official of the aid group said. At least 37 people were wounded and many patients and staff still missing, he added.

At the aid group’s bombed-out hospital, one wall of a building had collapsed, scattering fragments of glass and wooden door frames, and three rooms were ablaze, said Saad Mukhtar, director of public health in Kunduz. “Thick black smoke could be seen rising from some of the rooms ... The fighting is still going on, so we had to leave,” Saad said.

Almost 200 patients and employees were in the hospital, the only one in the region that can deal with major injuries, said MSF. “We are deeply shocked by the attack, the killing of our staff and patients and the heavy toll it has inflicted on healthcare in Kunduz,” operations director Bart Janssens said in a statement.

MSF said it gave the location of the hospital to both Afghan and US forces several times in the past few months, most recently this week, to avoid being caught in crossfire. The aid group said it had treated almost 400 patients in the 150-bed hospital since fighting broke out, most for gunshot wounds. So many patients have flooded in that the hospital had to put them in offices and on mattresses on the floor.

The International Committee of the Red Cross said it was “deeply shocked” by the incident. “This is an appalling tragedy,” said Jean-Nicolas Marti, head of the ICRC in Afghanistan. “Such attacks undermine the capacity of humanitarian organisations to assist the Afghan people at a time when they most urgently need it.”

The US military promised to investigate the incident, which could renew concerns over the use of its air power in the conflict. Afghan President Ashraf Ghani’s spokesman said last week there would be no airstrikes inside the city because of the risk of mass civilian casualties.

US forces launched an air strike at 2:15am local time, spokesman, Colonel Brian Tribus, said in a statement. “The strike may have resulted in collateral damage to a nearby medical facility ... This incident is under investigation,” he added.

Nato conceded US forces may have been behind the strike but has not so far commented on the specific claims of MSF, which has long treated the war-wounded from all sides of the conflict. The Afghan defence ministry claimed that militants were targeting troops from the hospital building.