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By Daniella Silva and The Associated Press

Three American soldiers were shot by an Afghan soldier on a base Sunday, the NATO-led Resolute Support mission in Afghanistan said.

Resolute Support said in a post on Twitter Sunday morning that the three U.S. soldiers were wounded after being shot by an Afghan soldier on a base in Helmand Province, Afghanistan.

The Afghan soldier opened fire on Sunday inside a base in the southern Helmand province and was shot dead, an Afghan official told the Associated Press.

Col. Mohammad Rasoul Zazai, an army spokesman, told the AP that the soldier had made a "mistake" and had not fired deliberately.

The American soldiers were receiving medical care, Resolute Support said in their post on Twitter.

The NATO mission in Afghanistan aims to train and advise Afghan security forces. Resolute Support follows the military mission in the country after combat operations concluded near the end of 2014.