Three foreign advisers and an Afghan interpreter have been killed in a suicide bomb attack outside Kabul International Airport.
The nationalities of the foreign advisers were not immediately clear.
The explosion comes days after one of the most audacious militant attacks in a year on the airport, which is used by both civilians and the military.
A Taliban spokesman said it had carried out the attack and claimed that 15 "invader" soldiers were killed or wounded.
At least five Taliban attackers were killed by Afghan security forces during the attack.
Kabul airport is home to a major operational base for NATO-led forces that have been fighting the Taliban for 12 years.
Security includes soldiers and police, guard towers and checkpoints.
Militants often fire rockets into the airport, causing little damage, but frontal attacks on the heavily guarded facility are rare and represent an ambitious target for insurgents.
Militants armed with rocket-propelled grenades attacked Kabul International Airport on 17 July.
The attack lasted about four hours after four unidentified militants opened fire on the airport from the roof of a building just to its north.