Story highlights The attack took place at an Afghan security forces compound in Helmand province

The identities of the two service members who were killed haven't been disclosed

Kabul, Afghanistan (CNN) Two NATO service members were killed Wednesday in southern Afghanistan after coming under fire from men wearing the uniforms of Afghan security forces.

NATO service members fired back, killing the attackers, the organization's Resolute Support Mission in Afghanistan said in a statement.

It didn't disclose the identities of the service members who were killed, saying that would be left to the relevant national authorities.

Afghan and NATO officials are still looking into the circumstances of the firefight, which took place early Wednesday at an Afghan security forces compound in the southern province of Helmand, the Resolute Support statement said.

It wasn't immediately clear if the attackers were members of the Afghan security forces or had obtained the uniforms by other means.

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