KABUL -- An Afghan soldier killed one U.S. Marine and wounded another before being shot to death in return fire Sunday in southern Afghanistan, the latest in a series of attacks against foreigners blamed on government forces within their own ranks.

Nearly 20 such attacks this year have raised the level of mistrust between the U.S.-led coalition and their Afghan partners as NATO gears up to hand over security to local forces ahead of a 2014 deadline for the withdrawal of combat troops.

The Afghan soldier opened fire on international troops in the Tarekh Naver in the Marjah district, a former Taliban stronghold that was the site of a major offensive by coalition forces in 2010, said a spokesman for the governor of Helmand province.

A senior U.S. defense official in Washington said Sunday that the victim was a U.S. Marine in Helmand province, and that one other Marine was wounded.

The provincial governor's spokesman, Daud Ahmadi, said the service member was killed in a gunfight between NATO forces and an Afghan army soldier, with one service member killed and another wounded.

Also Sunday, a NATO service member was killed by a bomb in eastern Afghanistan, the alliance said, raising to 139 the number of foreign troop deaths so far this year.

In another sign of deteriorating security in Afghanistan, the United States is considering abandoning plans for a consulate in the country's north because the building chosen was deemed too dangerous to occupy.

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