Three US contractors killed in "insider attack" in Afghanistan

KABUL: An Afghan soldier killed three US contractors and wounded a fourth on Thursday at Kabul´s military airport, an Afghan air force official said.

The Taliban claimed responsibility for the attack saying a militant infiltrator had carried it out.

The Afghan air force official said it was not clear why the attacker had killed the advisers."No one else was there to tell us the reason," the official told Reuters on condition of anonymity because he was not authorised to speak to the media.

"An investigation has been opened."

The international force in Afghanistan confirmed the shooting took place on Thursday evening. It also confirmed that one Afghan had been killed but it did not specify that he was the attacker.

Despite the introduction of new measures, including a requirement that coalition forces be armed at all times and stricter vetting procedures for Afghan security members, incidents continue to occur sporadically.