Three children were killed in a drone strike that US officials said struck a vehicle carrying so-called Islamic State suicide bombers, an Afghan official said.

The official spoke on condition of anonymity out of security concerns.

US officials said the vehicle was carrying explosives and that the initial strike on Sunday set off secondary explosions.

The US officials said the bombers planned to attack Kabul’s international airport, where a massive airlift is still under way ahead of a Tuesday deadline for the withdrawal of US forces.

The strike came as the US winds down a historic airlift that saw tens of thousands evacuated from Kabul’s international airport, the scene of much of the chaos that engulfed the Afghan capital since the Taliban took over two weeks ago.

After the Isis-K affiliate’s suicide attack that killed more than 180 people, the Taliban increased security around the airfield as the UK ended evacuation flights on Saturday.

US military cargo planes continued their runs into the airport on Sunday, ahead of a Tuesday deadline earlier set by President Joe Biden to withdraw all troops from America’s longest war.

However, Afghans remaining in the country worry about the Taliban reverting to their earlier oppressive rule.

Taliban spokesman Zabihullah Mujahid earlier said in a message to journalists that the US strike targeted a suicide bomber as he drove a vehicle loaded with explosives.

Two American military sources earlier called the air strike successful.

They said it caused “significant secondary explosions” indicating the presence of a substantial amount of explosive material in the vehicle.

The strike was the second by America since the airport suicide bombing.

On Saturday, a strike in Nangarhar province killed an IS member believed to have been involved in planning attacks against the US in Kabul.

The strike killed one person, Navy Captain William Urban said.