A U.S. soldier was killed and two others wounded in an "apparent insider attack" in southern Afghanistan on Saturday, NATO said.
"The wounded service members, who are in stable condition, are currently being treated," NATO's Resolute Support mission in Afghanistan said in a statement.
NATO did not release the identity of the American soldier killed or provide further details about the incident.
The shooting happened at the airport in Tarinkot, the capital of Uruzgan province, a local police officer told AFP.
That information could not be immediately verified by Afghan or NATO officials.
The Taliban said on Twitter that "a patriot Afghan soldier opened fire on Americans in Uruzgan airport killing and wounding at least four American invaders."
Insider attacks, often known as "green on blue" attacks in which Afghan service members or attackers wearing Afghan uniforms fire on U.S. or coalition troops, have been a regular feature of the conflict in Afghanistan, although their frequency has diminished in recent years.
Last year, the United States added thousands of additional troops to its forces in Afghanistan, which are engaged in both training and advising Afghan forces and conducting counterterrorist missions against Daesh and other militant groups.
As in other areas of the war, Afghan units suffer more heavily than coalition units from insider attacks. A Pentagon report last month said there were 47 so-called "green-on-green" attacks, or incidents where Afghan soldiers turn on their own side, so far this year.