The US military says it believes it has killed a planner for the Afghan branch of the Islamic State group in a drone strike in the east of the country.

The suspected member of the IS-K group was targeted in Nangarhar province.

IS-K said it had carried out an attack outside Kabul airport on Thursday that may have killed as many as 170 people, including 13 US troops.

A mass airlift has been under way at the airport since Taliban militants overran the capital this month.

In the past two weeks, more than 100,000 people are believed to have been evacuated, with the deadline set by the US for its forces to leave Afghanistan expiring on Tuesday.

President Joe Biden promised on Friday to hunt down the jihadists behind Thursday's suicide bombing.

IS-K, or Islamic State Khorasan Province, is the most extreme and violent of all the jihadist militant groups in Afghanistan.

The US drone strike is the first reported in Afghanistan since Thursday's blast.

Capt Bill Urban of Central Command said: "The unmanned airstrike occurred in the Nangarhar province of Afghanistan. Initial indications are that we killed the target. We know of no civilian casualties."

He described it as an "over-the-horizon counterterrorism operation".

A Reaper drone, launched from the Middle East, struck the militant while he was in a car with another IS member, killing them both, an official told Reuters news agency.

Most of IS-K's several thousand extremists are believed to be in hiding in the province, east of Kabul.

Twin bombs exploded near the perimeter of Kabul airport, hours after warnings from Western governments.

Thursday's blast outside Kabul airport tore through crowds of men, women and children.

Dozens of Afghans trying to leave the country were killed. In addition to the US personnel killed, two British nationals and the child of a British national were among the dead.

"We will not forgive, we will not forget. We will hunt you down and make you pay," Mr Biden warned the perpetrators on Friday.

He said another attack in Kabul was likely in the coming days.

Roughly 5,000 US troops are still stationed at Kabul airport, processing people desperate to leave.

"We are providing swift passage to every foreigner to leave Afghanistan in the next 48 hours," an unnamed Western official told Reuters.

Taliban officials say they have taken control of parts of the airport but the US says its forces are still in charge.

The BBC's chief international correspondent Lyse Doucet, who is in Kabul, has been told by sources that the US and British troops are "wrapping up" at the airport, and that the Taliban will take over in "a matter of hours".

Most Nato countries have now ended their emergency flights. France ended its evacuation effort on Friday, blaming deteriorating security at the airport.

American officials have issued a new warning to US citizens to stay away from the airport's gates in case of further attacks.

Pentagon spokesman John Kirby said the US believed there were still "specific, credible" threats against the airport.

"We certainly are prepared and would expect future attempts," he said.