At least three U.S soldiers were killed and another wounded during a joint U.S-Afghan military operation in eastern Nangarhar province on Saturday, the U.S officials confirmed to CNN.

The soldiers were shot in an apparent insider attack, also known as a "green-on-blue" because of the color-coding system used by NATO, a U.S official told CNN.

The shooter in Saturday's incident was believed to be a member of the Afghan military, the U.S official said.

The shootings occurred in the Achin district of the province, where U.S and Afghan troops have been carrying operations against Daesh insurgents.

The Taliban has claimed responsibility for the attack added that “an Afghan army soldier attacked the U.S soldiers in the district.”

In the meantime, a U.S military spokesman in Afghanistan told CNN "we are aware of an incident in eastern Afghanistan. We will release more information when appropriate."