Kabul Airport Explosion Appears to Be Suicide Attack, U.S. Officials Say

An explosion outside Kabul's airport amid a huge evacuation effort from Afghanistan appeared to be caused by a suicide bomb, U.S. officials said on Thursday, citing an initial report and cautioning that it could change.

Pentagon Press Secretary John Kirby confirmed in a Twitter post that there had been an explosion outside the airport in Afghanistan's capital.

A U.S. official told Reuters there were casualties from the explosion, but said it was unclear how many people were hurt. As many as three U.S. service members were among those injured, the official said, citing initial information.

Two U.S. officials said it appeared to be a suicide bombing.

A massive airlift of foreign nationals and their families as well as some Afghans has been under way since the day before Taliban forces captured Kabul on Aug. 15, capping a swift advance across the country as U.S. and allied troops withdrew.