The Taliban has claimed responsibility for a fatal bomb blast at the NATO air base at Bagram, north of the Afghan capital Kabul.
Authorities say four people have been killed and more than a dozen injured.
The bomber detonated a device close to a sports facility where officers and soldiers were exercising.
Authorities say it is unclear if a suicide bomber carried out the attack.
An investigation is underway as to uncover how the base, home to around 14,000 people, had its security compromised.