The US investigation into a deadly air strike on a Doctors Without Borders (MSF) hospital in Afghanistan showed a "frightening catalogue of errors" by American troops, the charity said Wednesday.

The October 3 air raid on the French charity's hospital during a Taliban offensive in the northern city of Kunduz killed at least 30 people, sparked an avalanche of global condemnation and forced the facility — the only trauma centre in the region — to close.

"The frightening catalogue of errors outlined today illustrates gross negligence on the part of US forces and violations of the rules of war," said MSF general director Christopher Stokes, responding to the earlier release of a US investigation into the attack that described it as "caused primarily by human error".

The US commander in Afghanistan John Campbell gave details of the US inquiry earlier Wednesday, describing how a Special Operations AC-130 gunship aircraft hit the hospital instead of a nearby Afghan intelligence compound that was thought to have been commandeered by Taliban fighters.

Campbell blamed the catastrophic accident in part on fatigue of US troops who had been battling the militant offensive in Kunduz for five days, adding that the mistake was "compounded by process and equipment failures".

Human, technical errors to blame for Afghan hospital strike: NYT
Kabul (AFP) Nov 25, 2015 –

US forces who launched an air strike on an Afghan hospital last month intended to attack a nearby Taliban-controlled compound, military officials told American media, citing an investigation set to blame human and technical error for the deadly strike.

The October 3 air raid on a Doctors Without Borders (MSF) hospital in the Taliban-held northern city of Kunduz killed at least 30 people, sparked an avalanche of global condemnation and forced the French charity to close the hospital.

Two military officials told the New York Times Tuesday that a combination of human and technical errors meant that a Special Operations AC-130 gunship aircraft hit the hospital instead of an Afghan intelligence compound hundreds of feet away that was thought to have been commandeered by Taliban fighters.

The gunship's crew relied on location information relayed to them by US and Afghan special forces rather than their aircraft's instruments, according to the officials, who discussed the report on condition of anonymity ahead of its formal release.

The findings will be officially announced by US General John Campbell at NATO headquarters in Kabul at 7.00 pm Wednesday (1430 GMT).

The officials' account as quoted by the NYT does not address why the attack — which lasted more than one hour — was not halted despite frantic telephone calls from MSF staff, nor why US ground forces failed to intervene when they saw the wrong building being hit.

One official told the Times the crew did not receive a full preflight briefing that would have told them the Kunduz hospital was protected under the Geneva Convention.

The US military also failed to follow its own rules of engagement for calling air strikes — that American or Afghan troops must be in extreme danger — while the Special Operations Forces did not positively identify that the area targeted was legitimate, the paper said.

"There was certainly some confusion over what they were shooting at," an official told the Wall Street Journal, which received a similar briefing. "If there wasn't, then this wouldn't have happened."

The US military offered a series of shifting explanations for the bombing raid before President Barack Obama admitted in a call to MSF chief Joanne Liu that the strike was a mistake and apologised.

A NATO statement released hours after the attack on Saturday, October 3 would not confirm the hospital was targeted, characterising it instead as "collateral damage" as Afghan forces came under fire.

The next day the US confirmed the hospital was hit directly, but did not offer further details.

Later General Campbell suggested that Afghan forces had called in the strike, before offering a fourth account in four days admitting US special forces had been in touch with the aircraft.

NATO and the Afghan army are conducting their own investigations.

MSF has called for an independent international investigation, saying the attack could be determined to be a "war crime".