A man wearing an Afghan National Security Force uniform opened fire on international soldiers at Kandahar Airfield Tuesday, killing one and wounding at least seven, a senior defense official said.
The shooter was initially able to escape after the attack, which happened at a security gate at the airport.
However, the International Security Assistance Force said later that he had been detained.
Afghan and international forces were conducting an investigation, and more details would be released as appropriate, ISAF added.
In a separate incident in Herat, western Afghanistan, 12 women, 4 children and a man were killed by a roadside bomb, a local official said.
There has been concern for some time over so-called "green-on-blue" attacks. In May, two American troops were killed when an Afghan soldier turned his weapon on them.
In August last year, U.S. military personnel were ordered to have a fully loaded magazine in their weapons at all times because of a spike in such attacks.
NBC News' Melissa Preen and Ian Johnston contributed to this report.