NATO says four U.S. service members have been killed in a roadside bomb explosion in southern Afghanistan.
A statement from NATO's International Security Assistance Force said the explosion took place Saturday, but did not give further details on the location or the victims' branch of service.
The deaths are the first U.S. fatalities attributable to hostile action in Afghanistan this year. One U.S. service member has died of non-combat causes so far in 2010.
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