"An International Security Assistance Force service member and an ISAF civilian contractor died following a suspected insider attack in eastern Afghanistan," the ISAF said in a news release said Sunday
There were varying descriptions of what happened Saturday afternoon at an Afghan military checkpoint in Wardak province, west of Kabul, but officials said three Afghans also died in the firefight, The New York Times said.
Regional spokesman Shahidullah Shahid said, "A clash ensued between two sides following a misunderstanding."
Insider attacks have killed 53 U.S. troops this year. The spate has led to U.S. and NATO allies reviewing past and present police and military recruits to weed out those who might turn on them and attack.
About the same number of Afghan soldiers and police officers have also been killed by insider attacks, which is harming morale and creating distrust within the ranks, Khaama Press said.
The U.S. military death toll since 2002 in Afghanistan rose to 2,000 following Saturday's battle, the newspaper said.