TEMPO.CO, Jakarta - The United States attacked an Islamic State (ISIS) "planner" in Afghanistan in retaliation for a deadly bombing outside Kabul airport and said there was a high risk of further blasts as it nears the end of a mission to evacuate civilians and withdraw troops.

Among the scores killed in Thursday's suicide bomb blast, claimed by an ISIS affiliate in the country, were 13 U.S. service members, the most lethal incident for U.S. troops in Afghanistan in a decade.

U.S. Central Command said on Friday the overnight drone strike took place in Nangarhar province, east of Kabul and bordering Pakistan.

"Initial indications are that we killed the target. We know of no civilian casualties," a U.S. military statement said.

Spokesmen for the Taliban, which completed a rapid takeover of the country this month as U.S. forces withdrew, declined to comment on the drone strike. The Islamic State group in Afghanistan is an enemy of the Taliban as well as the West and the Taliban has said it arrested some suspects after the blast.

Up to 170 people, not including the U.S. troops, were killed in the bombing, according to U.S. media including the New York Times, citing health officials. read more

The White House said the next few days were likely to be the most dangerous of the U.S. evacuation operation that the Pentagon said has taken about 111,000 people out of Afghanistan in the past two weeks

Pentagon spokesman John Kirby said the United States believed there were still "specific, credible" threats against the airport after the bombing at one of its gates.

"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."

The U.S. Embassy in Kabul warned Americans to avoid Kabul's airport because of security threats and those at its gates should leave immediately.

U.S. and allied forces have been racing to complete evacuations of their citizens and vulnerable Afghans and to withdraw from Afghanistan by the Tuesday deadline set by President Joe Biden after two decades of American military presence there.

Most of the more than 20 allied countries involved in airlifting Afghans and their citizens out of Kabul said they had completed evacuations by Friday.

Britain will end its operation on Saturday, its armed forces chief said, while acknowledging that it, like other countries, had not been able to get everyone out.

Biden said earlier he had ordered the Pentagon to plan how to strike ISIS-K, the Islamic State affiliate that claimed responsibility for Thursday's bombing.

Afghanistan's Islamic State affiliate, known as Islamic State Khorasan (ISIS-K) after an old name for the region, appeared in eastern Afghanistan in 2014 and later made inroads into other areas, particularly the north.

Read: Indonesia Condemns Terrorist Attacks Near Kabul Airport

REUTERS