An Afghan policeman wounded at least two foreign soldiers when he opened fire on troops from the US-led NATO mission on Monday, officials said, adding to a spike in such attacks.
The shooting took place in Achin, a remote district in the eastern province of Nangarhar, local police chief Abdullah Azim Stanikzai told AFP. NATO confirmed the incident but gave no details.
The majority of NATO troops in Nangarhar are American.
The shooter escaped unhurt but an Afghan intelligence officer was wounded when coalition soldiers returned fire, Stanikzai added.
Seven soldiers of the US-led International Security Assistance Force (ISAF) lost their lives over four days last week when Afghan forces turned weapons on their NATO allies.
According to NATO, 37 of its soldiers have died in 27 such attacks so far this year, up from 21 incidents and 35 deaths in all of 2011.
Taliban spokesman Zabihullah Mujahid claimed responsibility for Monday's attack and said the gunman was with the militia. "He's a brave Afghan. He's with us," Mujahid told AFP by telephone.
Stanikzai said the policeman had just returned from leave.
"He was on vacation but had just returned to duty. He grabbed a weapon from a colleague and opened fire," he added. He said a hunt to arrest him was under way.
An ISAF spokesman, Lieutenant Colonel Hagen Messer, said "a man wearing civilian clothes fired at ISAF-ANSF troops", using the acronym for Afghan security forces.
"The shooter was a member of the Afghan uniform police," Messer said, confirming the injuries.
Although the Taliban often claim credit, Afghan and Western officials say most attacks are motivated by cultural differences between troops fighting the Taliban side by side.
Known as "green on blue", there has been a dramatic spike in such attacks in recent months.
On Friday, two such incidents killed six Americans in the southern province of Helmand. One of the shooters was a man in police uniform and the other a civilian staff member on a joint Afghan-NATO base.