Afghanistan – The United States has conducted an airstrike on a member of an Islamic State affiliate in response to Thursday's deadly attack at Kabul airport.

A planner for ISIS-K was targeted in the drone strike in Afghanistan's Nangarhar province, US Central Command spokesperson Bill Urban said early Saturday.

"Initial indications are that we killed the target. We know of no civilian casualties," he said.

It was not initially clear whether the target was directly involved in the airport attack in the Afghan capital.

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The Islamic State affiliate in Afghanistan, called Islamic State Khorasan, or ISIS-K, claimed responsibility for the Kabul airport bombing that killed dozens of people, including 13 US soldiers.

US President Joe Biden had previously warned he would seek retribution for the attack.

"We will not forgive, we will not forget, we will hunt you down and make you pay," Biden said Thursday.

Meanwhile, the forces that remain in Kabul are on high alert for further terror threats.

The White House has said the coming days will be the most dangerous in the evacuation mission, but Biden emphasized Friday the US would continue to fly people out.

The US embassy in Afghanistan issuing a renewed security warning for its citizens at Kabul's airport early Saturday.

All US citizens at the airports Abbey gate, East gate, North gate, or the New Ministry of Interior gate should leave immediately, the embassy said in its update.

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Advice for all US citizens to avoid travel to the airport remained in place.

Washington and allied countries are rushing to complete their evacuations and troop withdrawals by August 31, a deadline agreed with the Taliban, which took power in the country earlier this month.

Washington is processing evacuees at several military installations across Europe and the Middle East before resettlement in the US.

As of Friday, the US said it had evacuated around 110,000 people since the mission began in mid-August.

Around 500 US citizens who want to leave are still in Afghanistan. The US State Department said it was in touch with them and hundreds more nationals who were undecided on whether to leave.