NATO says two of its troops have been killed in southern Afghanistan. The military alliance says in a statement the troops were killed Wednesday in a "hostile incident." It did not provide details on their nationalities or say how they were killed. Southern Afghanistan is the center of the Taliban-led insurgency, where thousands more US troops will join the fight later this year. More than 6,400 people were killed in 2008, according to an Associated Press count of figures released by Afghan and Western officials.