Details of the shooting incident remained unclear, said the official, who spoke on condition of anonymity. The victims were employed under a US Defense Department contract and died from gunshot wounds.
Western troops and civilians training Afghan security forces have faced lethal assaults from Afghans in uniform who turn their guns on their counterparts.
NATO troops have adopted special security measures in recent years to try to counter the threat.
The airport in the Afghan capital Kabul is heavily guarded, with one section devoted to commercial aircraft and another area set aside for a NATO contingent.
Thursday's attack came after a surge in violence by the Taliban insurgency over the past year.
At least nine people were killed earlier Thursday in the country's east when a suicide bomber detonated an explosive at a funeral for victims of a roadside bomb attack.
Most NATO combat troops pulled out of Afghanistan last year but a small contingent of about 12,000 remains in the country, including roughly 10,600 American forces.
The American soldiers, along with other NATO troops and private contractors, are helping the Afghans improve their logistics and build up a fledgling air force.
COMMENTS (3)
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O yeah and uncle sam will be back . like He did in Iraq.
OK here goes,
Did anyone ever consider that by trying to stabilize Afghanistan is a lost cause. As an ex-soldier, I am far too familiar with these stories. We are not welcome there,period. No more than foreign armies would be embraced on any sovereign soil.
We are seeing now a second generation of people (since1991 the gulf war) who have grown up despising western ideology and culture. Add in centuries old blood feuds, religious fanaticism and a propensity towards barbarism and i find it quite difficult to see any peaceful resolution.
It's time we pull back and stop burying our friends,sons and daughters in the middle East. our economies have been decimatedby our ongoing participation in these conflicts. As well, we are nurturing a global image that every westerner supports this type of intervention. Remember Viet nam. At home joblessness,poverty and the security must be our focus. The general public have no idea what is happening there. There is a unification by religious beliefs. All alliances are inevitably doomed to failure.
It is very disheartening to see the suffering that our countries have caused. Purposely we have created and nurtured a culture of fear, creating power voids that have allowed such evil to manifest itself.
Don't ever forget War is big business. Trillions of dollars spent with not even a consideration for our own people. Americans suffer everyday and struggle. How can we be so blind and indifferent to our own sons.
Our basic freedoms and the country we are so proud of were born of vision, necessity, and it was the people that rose up for there own liberty. That is necessary for the people to see and do for themselves. Stop burying our children.
History will write itself without us manipulating its course. We have to accept that these regions will always be in turmoil, merely based on historical fact.
The new phenomenon of contractors making vast fortunes off conflict sickens me