THE PENTAGON HAS retreated from its defence of a drone strike that killed multiple civilians in Afghanistan last month, announcing an internal review revealed that only civilians were killed in the attack, not an Islamic State extremist as first believed.

“The strike was a tragic mistake,” Marine General Frank McKenzie, head of US Central Command, told a Pentagon news conference.

For days after the August 29 strike, Pentagon officials asserted that it had been conducted correctly, despite numerous civilians being killed, including children.

News organisations later raised doubts about that version of events, reporting that the driver of the targeted vehicle was a long-time employee at an American humanitarian organisation and citing an absence of evidence to support the Pentagon’s assertion the vehicle contained explosives.

Gen McKenzie said the vehicle was struck “in the earnest belief” that it posed an imminent threat.

“I am now convinced that as many as 10 civilians, including up to seven children, were tragically killed in that strike,” Gen McKenzie said.

“Moreover, we now assess that it is unlikely that the vehicle and those who died were associated with Isis-K, or a direct threat to US forces,” he added, referring to the Islamic State group’s Afghanistan affiliate.

Gen Mark Milley, chairman of the Joint Chiefs of Staff, told reporters two days after the attack that it appeared to have been a “righteous” strike and that at least one of the people killed was a “facilitator” for the Islamic State group’s Afghanistan affiliate, which had killed 169 Afghan civilians and 13 American service members in a suicide bombing on August 26 at Kabul airport.

After Gen McKenzie’s remarks, Gen Milley expressed regret.

“This is a horrible tragedy of war and it’s heart wrenching,” Gen Milley told reporters traveling with him in Europe.

“We are committed to being fully transparent about this incident.”

“In a dynamic high-threat environment, the commanders on the ground had appropriate authority and had reasonable certainty that the target was valid, but after deeper post-strike analysis our conclusion is that innocent civilians were killed,” Gen Milley added.

Accounts from the family, documents from colleagues seen by The Associated Press, and the scene at the family home — where Zemerai Ahmadi’s car was struck by a Hellfire missile just as he pulled into the driveway — all painted a picture of a family that had worked for Americans and were trying to gain visas to the United States, fearing for their lives under the Taliban.

The family said that when the 37-year-old, alone in his car, pulled up to the house, he honked his horn. His 11-year-old son ran out and Mr Zemerai let the boy get in and drive the car into the driveway. The other kids ran out to watch, and the Hellfire missile incinerated the car, killing seven children and an adult son and nephew of Mr Zemerai.

The airstrike was the last of a US war that ended as it had begun in 2001 — with the Taliban in power in Kabul.

The speed with which the Taliban overran the country took the US government by surprise and forced it to send several thousand troops to Kabul airport for a hurried evacuation of Americans, Afghans and others.

The evacuation, which began on August 14, unfolded under a near-constant threat of attack by the Islamic State group’s Afghanistan affiliate.