A Taliban spokesman said a U.S. drone strike targeting a suspected suicide bomber in Kabul on Sunday resulted in civilian casualties and condemned the United States for failing to inform the Taliban before ordering the strike.

Spokesman Zabihullah Mujahidtold China's state television CGTN on Monday that seven people were killed in the drone attack, describing the U.S. action on foreign soil as unlawful.

"If there was any potential threat in Afghanistan, it should have been reported to us, not an arbitrary attack that has resulted in civilian casualties," Mujahid said in a written response to CGTN.

Pentagon officials said the suicide car bomber had been preparing to attack the airport in Kabul, where U.S. troops were in the final stages of a withdrawal from Afghanistan, on behalf of ISIS-K, a local affiliate of Islamic State that is an enemy of both the West and the Taliban.

U.S. Central Command said it was investigating reports of civilian casualties from Sunday's drone strike.

"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," it said.

Mujahid had issued a similar condemnation of a U.S. drone strike on Saturday that killed two Islamic State militants in the eastern province of Nangarhar. He said two women and a child were wounded in that attack.