Five US troops killed in Afghanistan: Pentagon

Five service members of the US troops were killed Monday in a possible friendly fire during a security operation in Afghanistan, the Pentagon said Tuesday.

Investigators were looking into the likelihood that friendly fire was the cause, Xinhua quoted Pentagon Press Secretary Rear Adm. John Kirby as saying 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 US 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.

Over 52,000 coalition troops, down from the peak of 130,000 in 2010, are stationed in Afghanistan, and the US plans to reduce its forces to less than 10,000 next year.