"There was a shooting incident at an annex of the US embassy in Kabul involving an Afghan employee who was killed," said US embassy spokesman Gavin Sundwall.
"One US citizen was killed, one was wounded." Sundwall said the Afghan employee was behind the attack and that he had acted as "a lone gunman." "The motivation for the attack is still under investigation," he added.
The incident took place last night inside the Ariana Hotel compound, an annex to the US embassy. An Afghan government official speaking anonymously to AFP said the Ariana compound was used by the CIA.
The injured person, whose injuries Sundwall said were "not life-threatening," was evacuated to a military hospital in Afghanistan for treatment following the attack.
The body of the dead American is expected to be returned to the United States soon. Sundwall declined to comment on whether the building was a CIA facility.
"I'm sure there will be an investigation. We take our security very seriously and it is under constant review," he said.
Kabul has seen escalating violence in recent weeks with a 19-hour siege targeting the US embassy and former president Burhanuddin Rabbani assassinated.