KABUL -- Two U.S. soldiers have been killed and six wounded in a firefight in Afghanistan's eastern Nangarhar Province, with the U.S. military saying initial reports indicate an attack was carried out by a man in an Afghan National Army (ANA) uniform.



Colonel Sonny Leggett, a spokesman for U.S. forces in Afghanistan, said in a statement early on February 9 that the incident occurred after a combined U.S.-Afghan force was returning from a "key-leader engagement" in which U.S. forces meet with important individuals of selected areas.



"Current reports indicate an individual in an Afghan uniform opened fire on the combined U.S. and Afghan force with a machine gun," Leggett said.



"We are still collecting information, and the cause or motive behind the attack is unknown at this time," he added.



Shah Mahmood Miakhel, the governor of Nangarhar Province, earlier told RFE/RL that at least three Afghan soldiers were injured in the attack that he also said appears to have been carried out by an assailant in an ANA uniform.



He added that the man had been killed and that his motive for the attack was not known.



Nangarhar Provincial Council member Ajmal Omer also told AP that the gunman was killed, adding that the incident took place in Nangarhar Province's Sherzad District.

The New York Times on February 8 quoted an unnamed U.S. military official saying there were at least six American casualties and confirmed that there were fatalities without saying how many.

Assaults by rogue Afghan soldiers -- so-called “green-on-blue” attacks -- became a regular occurrence in the conflict, although they have become less frequent in recent years.



"We are not ruling any possibility out, but we are not calling it an insider attack, Taliban attack, or 'green-on-blue' at this stage," an Afghan defense official told Reuters.



Sohrab Qaderi, a provincial council member in Nangarhar, said it was possible a “tactical mistake” occurred between Afghan and foreign forces.



U.S. spokesman Leggett said in a statement earlier that both Afghan and U.S. personnel were "engaged by direct firing."



The Taliban and an Islamic State (IS) affiliate both operate in eastern Nangarhar Province. Taliban sources could not immediately be reached for comment.



Some 14,000 U.S. troops are stationed in Afghanistan as part of the U.S.-led NATO mission to train, assist, and advise Afghan forces and to carry out counterterrorism missions.



Washington has conducted talks with the Taliban in Qatar in an effort to find an end to Afghanistan's 18-year war, but a deal has not yet been reached.



With reporting by AP, Reuters, and The New York Times