KABUL • Afghan forces called in a US air strike on a Kunduz hospital that killed 22 people, according to the top American commander in Afghanistan, after medical charity Medecins Sans Frontieres (MSF) branded the incident a war crime.
However, the United Nations said it would wait for the results of US, Nato and Afghan investigations before deciding whether to support an independent probe.
Monday's statement by General John Campbell marks the first US military acknowledgement it was behind last Saturday's devastating raid in the northern Afghan city.
But his remarks prompted MSF to blast the "discrepancies" in US accounts of the strike, which caused patients to burn to death in their beds and reduced the hospital to smouldering rubble.
"We have now learnt that on Oct 3, Afghan forces advised that they were taking fire from enemy positions and asked for air support from US air forces," Gen Campbell told reporters. "An air strike was then called to eliminate the Taleban threat and several civilians were accidentally struck."
His statement was at odds with previous US military claims that the strike was carried out to protect American special forces on the ground from enemy fire.
There was no immediate reaction from Afghan officials. But they have previously claimed that insurgents were using the hospital as a position to target soldiers and civilians.
Washington is under growing pressure to come clean over the strike, which occurred five days after the Taleban overran Kunduz in its most spectacular victory in 14 years.
MSF, which has closed the trauma centre that was seen as a lifeline in the war-battered region, accused Gen Campbell of passing the buck to the Afghan government.
"The reality is, the US dropped those bombs. It hit a huge hospital full of wounded patients and MSF staff," MSF general director Christopher Stokes said.
The group said Afghan and coalition troops were fully aware of the exact location of the hospital, having been given GPS coordinates of the facility, which had been providing care for four years.
The main building housing the intensive care unit and emergency rooms was "repeatedly, very precisely" hit almost every 15 minutes for more than an hour, MSF said.
Mr Stokes earlier also hit out at claims by Afghan officials that militants were inside the hospital.
"These statements imply that Afghan and US forces working together decided to raze to the ground a fully functioning hospital with more than 180 staff and patients inside because they claim members of the Taleban were present," he said. "This amounts to an admission of a war crime."
Mr Stokes called for an independent probe, saying "an internal investigation by a party to the conflict would be wholly insufficient".
UN human rights chief Zeid Ra'ad al-Hussein said last Saturday that, "if established as deliberate in a court of law, an air strike on a hospital may amount to a war crime".
Under international law, the bombing would be a war crime only if it was proved that the hospital was attacked intentionally, legal experts said.
UN Secretary-General Ban Ki Moon last Saturday called for an"impartial" investigation of the incident but he stopped short of saying that should be done by the UN.
A UN investigation is unlikely at this point because the US is viewed as capable of carrying out a credible investigation and because the incident is not viewed as part of a systematic campaign targeting civilians, diplomatic sources said.
The world body investigated Israeli attacks on UN schools amid charges that Hamas fighters hid weapons on UN premises during last year's war in the Gaza Strip, though that was because of the involvement of UN facilities.
Under US law, any grave breaches of the Geneva Conventions - including wilful killing or wilfully causing great suffering or serious injury to body or health - are considered a war crime.
It is not clear whether MSF plans to launch its own legal action.
US Defence Secretary Ashton Carter expressed sadness over the "tragic loss of life" and repeated President Barack Obama's promise of a full and transparent investigation.
AGENCE FRANCE-PRESSE, REUTERS