Gunman kills 3 NATO workers in Afghanistan

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Afghan boys read the Quran during the Muslim holy month of Ramadan at a mosque in the city of Jalalabad, the provincial capital of Nangarhar province, east of Kabul, Afghanistan, Sunday, July 22, 2011. Muslims from Morocco to Afghanistan are experiencing the toughest Ramadan in more than three decades with no food or drink, not even a sip of water, for 14 hours a day during the hottest time of the year. (AP Photo/ Rahmat Gul)

KABUL, Afghanistan (AP) — NATO says a person wearing an Afghan national security force uniform turned his weapon against civilian contractors working with the U.S.-led military coalition, killing three.

NATO said the attack occurred Sunday in western Afghanistan.

The coalition says the gunman was killed during the incident, which is still being investigated.

No further details or information about the civilians who died was released.

Afghan security forces or militants dressed in their uniforms have been killing a rising number of coalition forces, but they have not been specifically targeting contractors working for the coalition.

So far this year, 26 foreign troops have been killed in these types of attacks.