KABUL, Afghanistan (AP) Two gunmen wearing Afghan National Army uniforms turned their weapons on NATO troops Tuesday, killing an American service member and wounding two others, U.S. and coalition officials said.

The Taliban claimed responsibility for the shooting in eastern Afghanistan the latest in a rising number of so-called "green-on-blue" attacks in which Afghan security forces, or insurgents disguised in their uniforms, kill their U.S. or NATO partners.

The incidents have undermined the trust between U.S. and NATO forces and the Afghan troops who are taking over the responsibility of security in their nation as international combat units withdraw.

The international military coalition did not disclose the nationality of the service member killed, but a U.S. official said the victim was American.

A second U.S. official said two U.S. service members also were wounded in the attack. The official said the two gunmen were in custody.

The officials spoke on condition of anonymity because they were not authorized to disclose the information.

A coalition statement said Afghan and coalition officials were investigating the shooting.

So far this year, 27 coalition troops have been killed in 20 such attacks, according to an Associated Press tally. That compares with 11 fatal attacks and 20 deaths the previous year. In 2007 and 2008 there were a combined total of four attacks and four deaths.

Taliban spokesman Zabiullah Mujahid said in a statement to the media that one Afghan soldier killed nine U.S. troops, but the Taliban often exaggerate the death toll of their attacks. He said many other coalition troops were injured in the shooting, which occurred at 5 p.m. at a military base in Gerdiserai area of Paktia province. Afghan officials confirmed that the attack occurred in Paktia.

"The soldier who opened fire on the Americans had long been in contact with Taliban in the area," Mujahid said. "The soldier has escaped and has joined with the Taliban."