Another attack on Kabul airport is highly likely, US President Joe Biden has warned, saying that military commanders have told him it could come as early as Sunday.
The US is continuing evacuations but the final UK troops, diplomats and officials have now left Kabul.
About 170 people died after a suicide bomber targeted the airport on Thursday.
The IS-K group has claimed the attack.
In retaliation, the US carried out a drone strike on eastern Afghanistan late on Friday, killing two “high-profile” members of IS-K – the Islamic State (IS) group in Khorasan Province.
The two are described as a planner and a facilitator. It is unclear whether they were directly involved in planning the Kabul airport attack.
“This strike was not the last. We will continue to hunt down any person involved in that heinous attack and make them pay,” Mr Biden said in a statement released on Saturday.
IS-K is the most extreme and violent of all the jihadist militant groups in Afghanistan and has major differences with the Taliban, who now control most of the country. It accuses them of abandoning the battlefield in favour of a negotiated peace settlement with the Americans.
The Taliban condemned the air strike, saying the Americans should have consulted them first, a spokesman told Reuters news agency.