At least two NATO soldiers were killed following an attack by Afghan national army in eastern Afghanistan on Monday.

NATO-led International Security Assistance Force following a statement announced, “Two International Security Assistance Force service members died when a member of the Afghan National Army turned his weapon against ISAF service members in eastern Afghanistan today.”

The source further added, “ISAF troops returned fire, killing the ANA soldier who committed the attack. “

Afghan and ISAF officials are investigating the incident, ISAF said following the statement.

The source did not disclose further information regarding the exact location of the incident and nationalities of the deceased soldiers.

International Security Assistance Force generally do not disclosse identities of the NATO soldiers killed in Afghanistan saying, “It is ISAF policy to defer casualty identification procedures to the relevant national authorities.”

So far this year, 32 “green-on-blue” attacks (the phrase comes from the colors that the U.S. military assigns in exercises to “host nation” and “friendly” forces) have killed 40 members of coalition forces and wounded 69, versus 16 attacks that resulted in 28 dead and 43 wounded during the same period in 2011.