The Pentagon is due to release a report on an internal investigation into one of the most infamous episodes of the war in Afghanistan: a special operations airstrike on a hospital in the north of the country last year that left 42 civilians dead.

The report provides an official assessment of the failings that led to a US AC-130 gunship attacking a Kunduz hospital run by Médecins Sans Frontières (MSF), or Doctors Without Borders, several of whose patients burned to death in their beds. The organization has called the strike a deliberate act tantamount to a war crime.

Defense sources indicated declassification of the long-awaited report could come as soon as this week. In the fall, US officials said an unspecified number of officers involved in the strike had been suspended from duty.

Kunduz hospital attack: how a US military ‘mistake’ left 22 dead Read more

“Although no nation does more than the United States to avoid civilian casualties, in this particular incident, we did not meet our own high standards,” a senior Pentagon policy official, Brian McKeon, wrote to the nongovernmental organization Physicians for Human Rights last month.

Early US accounts of the 3 October strike shifted substantially, with the general in charge of the war at the time walking back a public claim that Afghan forces engaged in a firefight with the Taliban had called in the strike. That general, John Campbell, subsequently ordered an official investigation.

Campbell, in November, called the pre-dawn airstrike a “tragic but avoidable accident caused primarily by human error”.

According to his preliminary description of the investigation, although MSF had provided the US and Afghan authorities with the field hospital’s coordinates, the AC-130 crew, rushing to aid US forces in a days-long fight to dislodge the Taliban from Kunduz, launched before receiving a mission brief that would have identified the hospital.

An apparent on-board systems failure limited the gunship crew from communicating with officers below, a confusion compounded by the aircraft veering off-course to avoid a perceived missile threat. Campbell stated that the effect was that the AC-130 targeted the hospital under the incorrect assumption that the facility was a building that Afghan forces were clearing of insurgents. But he also said that the gunship crew, before the first salvo, relayed its targeting coordinates back to a headquarters in Bagram airfield, which failed to realize that the coordinates corresponded to a protected facility.

Campbell’s successor, John Nicholson, traveled to Kunduz last month to deliver a rare, personal apology, only the second known to have been offered by a senior military officer to Afghan civilians. In November, a spokesman for the command told reporters that an unspecified number of personnel involved in the strike “have been suspended from their duty positions”.

The spokesman, Brig Gen Wilson Shoffner, also indicated that launching an airstrike even on the intended target was a disproportionate response to the Taliban threat in Kunduz, saying: “The investigation found that the actions of the aircrew and the special operations forces were not appropriate to the threats that they faced.”

MSF declined to comment ahead of the investigation’s release, preferring to offer a reaction after the organization has had a chance to review the report.

The US did not consent to an independent investigation by an international body called the International Humanitarian Fact Finding Committee, as MSF had requested.

MSF has not reopened the hospital six months after the attack, saying it first needs “clear reassurances from all parties to the conflict” that they will hold hospitals, patients and medical staff off-limits to violence.

Susannah Sirkin, of Physicians for Human Rights, which has called for accountability surrounding the Kunduz airstrike, urged the Obama administration to consider a “criminal investigation” where appropriate.

“All reports to date indicate that this strike – and its devastating outcome – was the result of multiple failures at multiple levels within the military. PHR believes such a pattern may constitute gross negligence, and therefore the consequences of any investigation must go well beyond administrative punishment to include an examination of criminal liability,” Sirkin said.