The US has conducted a drone strike against an Islamic State target in Afghanistan on Saturday, as the airlift of those desperate to flee moved into its fraught final stages with fresh terror attack warnings and encroaching Taliban forces primed to take over the Kabul airport.

US troops overseeing the evacuation have been forced into closer security cooperation with the Taliban to prevent any repeat of a suicide bombing that killed scores of civilians crowded around one of the airport’s main access gates, and 13 American troops.

The attack was claimed by a regional chapter of the Islamic State – known as Islamic State Khorasan Province (ISKP) – and the Pentagon announced it had carried out a drone attack on a “planner” from the jihadist group in eastern Afghanistan.

“Initial indications are that we killed the target. We know of no civilian casualties,” the US military said in a statement.

US Central Command said the airstrike took place in Nangarhar province, east of Kabul and bordering Pakistan. It did not say whether the target was connected with the airport attack.

The White House said the next few days are likely to be the most dangerous as evacuations continue ahead of looming deadline for the withdrawal of US forces.

Just before details of the airstrike targeting Islamic State were made public, the US embassy in Kabul issued a fresh warning over security threats at the airport and called on US citizens at the gates to “leave immediately”.

It follows Pentagon spokesman John Kirby earlier saying the US believes there are still “specific, credible” threats against the airport.

“We certainly are prepared and would expect future attempts,” Kirby told reporters in Washington. “We’re monitoring these threats, very, very specifically, virtually in real time.”

US and allied forces are racing to complete evacuations of their citizens and vulnerable Afghans and to withdraw from the country by the Tuesday deadline set by the US president, Joe Biden, after two decades of American military presence there.

The Pentagon said the US has taken about 111,000 people out of Afghanistan in the past two weeks.

While some have been evacuated, many are still seeking to get out. Throngs of people have gathered outside the airport to try to get on to evacuation flights since the Taliban took control of Afghanistan on 15 August, although on Friday, Taliban guards stopped people from approaching.

The Islamic State affiliate that claimed responsibility for Thursday’s bombing appeared in eastern Afghanistan in 2014 and later made inroads into other areas, particularly the north.

The group is an enemy of the Islamist Taliban as well as the west. The Pentagon said Thursday’s attack was carried out by one suicide bomber at an airport gate, not two as it had earlier stated.

Biden said earlier he had ordered the Pentagon to plan how to strike ISKP. A US official, speaking on the condition of anonymity, said the drone strike was against an Islamic State militant planning attacks.

A reaper drone, which took off from the Middle East, struck the militant while he was in a car with an Islamic State associate, the official said. Both are believed to have been killed, the official added.

A senior Taliban commander said some ISKP members had been arrested in connection with the Kabul attack. “They are being interrogated by our intelligence team,” the commander said.