US officials stated that an American service member was killed and others were wounded when attackers dressed as Afghan police officers opened fire on them in Afghanistan on Monday, according to the Associated Press.
The three attackers fled after the so-called "green-on-blue" or insider attack, said Agence France Presse.
The death of the NATO member takes the toll of such attacks on Western forces by Afghan allies to 23, according to AFP.
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"The International Security Assistance Force confirms that three individuals in Afghan police uniforms turned their weapons against coalition service members in southern Afghanistan yesterday, killing one ISAF service member," said NATO's International Security Assistance Force, in a statement, reported AFP.
Jamie Graybeal, a spokesman for ISAF, confirmed the death to the AP, and said the shooters were being sought.
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It remained unclear whether they were actually Afghan forces or had just obtained uniforms.
CNN reported that as many as eight or nine others were wounded in the attack.
The ISAF force in Afghanistan is training its Afghan counterparts to take over security for the nation when foreign troops are scheduled to withdraw in 2014, said the BBC.