A brief announcement on NATO's International Security Assistance Force website said coalition and Afghan officials were assessing the attacks to determine the facts but gave no other details such as the nationality of the victims.
A Voice of America report said four others were injured in the shootings which occurred in Kapisa province, north of Kabul.
The New York Times, quoting officials, said the attacks were on American-led coalition soldiers.
The Times report also said the attack was the first such reported insider or the so-called green-on-blue attack this year.
The frequency of such incidents in which men in green Afghan uniforms turn on their coalition force partners has come down significantly since 2012, when the issue had become a major security concern for coalition force commanders, forcing them to take a number of preventive measures.
In 2012, such green-on-blue attacks killed 64 coalition soldiers. Last year, there were 16 such deaths.
The Times said another reason for the decline in such attacks is also because of the number of the international forces in Afghanistan has come down under the U.S.-led NATO troop withdrawal program. The report said NATO has virtually ended its joint combat operations with Afghan troops, devoting its effort instead largely to training Afghan forces.
On Monday, the ISAF said a NATO soldier died in eastern Afghanistan during a fire fight with enemy forces. On the same day, two ISAF contracted-civilians died in an improvised explosive device explosion also in eastern Afghanistan. No details about either of the incidents were available.