An Afghan wearing a security forces uniform shot dead three foreign special forces personnel on Saturday and wounded another, Afghan and Western military officials said, in the first apparent "insider attack" in several months.
Since last year, attacks by Afghan soldiers on their allies in the NATO-run ISAF force have become a serious problem, threatening to further undermine waning support for the war among Western nations sending troops here.
"Three International Security Assistance Force service members died when an individual wearing an Afghan National Security Forces uniform shot them in eastern Afghanistan today," ISAF said in a statement.
An Afghan official, speaking on condition of anonymity, said the three soldiers killed were special forces, though he declined to provide their nationality.
U.S. forces provide the bulk of ISAF troops in the east. The attack was the seventh reported insider attack this year, and 12 ISAF personnel have been killed.
The last reported insider attack was on July 9, when an Afghan soldier at a military base in Kandahar shot dead one soldier and wounded three others.
"We can confirm that three ISAF service members were killed and one wounded by an individual wearing an ANSF uniform in Gardez," said Afghan Defence Ministry spokesman General Zahir Azimi.
The attack was shot dead by Afghan soldiers immediately after the attack, Azimi said.
Gardez is the capital of eastern Paktia, a volatile province that shares a porous border with Pakistan and is a hub for the Haqqani network, an insurgent group associated with the Taliban.
Azimi said the ministry was investigating the incident.
Last year saw a record number of such attacks. Figures have dropped considerably this year, partly due to increased security and partly due to a reduction in the interaction between Afghan soldiers and their foreign counterparts, Western officials have said.