WASHINGTON, June 10 (Xinhua) -- Five service members of U.S. troops were killed on Monday in a possible friendly fire during a security operation in southern Afghanistan, the Pentagon said on Tuesday.
Investigators were looking into the likelihood that friendly fire was the cause, Pentagon Press Secretary Rear Adm. John Kirby said in a statement. "Our thoughts and prayers are with the families of these fallen."
The deaths bring to 39 the number of the NATO forces killed so far this year in Afghanistan.
The incident occurred during a security operation when the U.S. service members' unit came into contact with enemy forces, the NATO-led International Security Assistance Force officials said in a statement issued from the command's headquarters in Kabul, Afghanistan.
"Tragically, there is the possibility that fratricide may have been involved," the statement said. "The incident is under investigation."
More than 52,000 coalition troops, down from the peak of 130, 000 in 2010, are stationed in Afghanistan, and the United States plans to trim its forces to less than 10,000 next year.