Gunmen dressed in Afghan military uniforms shot and killed two NATO service members in southern Afghanistan on Wednesday, officials said. The NATO service members fired back and killed the attackers, according to a statement from the NATO Resolute Support Mission in Afghanistan. Officials declined to reveal the nationalities or identities of the soldiers. Afghan and NATO officials are still investigating the attack and whether the gunmen were members of Afghan security forces or had taken the uniforms by other means. The Resolute Support Mission replaced NATO’s formal combat mission last year to train and support Afghan forces. The attack follows Saturday’s suicide bombing in Kabul that killed at least a dozen people, including three U.S. contractors.