The statement came after CNN reported that nine members of a family, including six children, were killed in Sunday's air strike in the crowded capital, where thousands of Afghans are still trying to flee the Taliban.

AFP has not been able to confirm the report. Local media also reported that civilians were killed in the strike.

"We are aware of reports of civilian casualties following our strike on a vehicle in Kabul today," Captain Bill Urban, a CENTCOM spokesman, said in a statement.

"We are still assessing the results of this strike, which we know disrupted an imminent ISIS-K threat to the airport," he continued, using an acronym for the Afghan branch of the Islamic State group, which carried out a suicide attack at the airport on Thursday.

"We know that there were substantial and powerful subsequent explosions resulting from the destruction of the vehicle, indicating a large amount of explosive material inside that may have caused additional casualties," Urban continued. "It is unclear what may have happened, and we are investigating further.

"We would be deeply saddened by any potential loss of innocent life," he said.

The US air strike came after a suicide bomber from the Islamic State group on Thursday targeted US troops stopping huge crowds of people from entering the airport as they try to flee the new Taliban regime.

Scores of people died in the attack, including 13 US service personnel.

The car that was destroyed by the US strike had been headed for Kabul's airport, a Taliban spokesman had said earlier Sunday.

About 114,000 people have been evacuated since August 15, when the Taliban swept back into power. The American withdrawal from Afghanistan is due to be completed by Tuesday.