Two U.S. troops killed by Afghan gunmen

Two U.S. troops were killed by Afghan gunmen on Thursday, the third shooting incident involving U.S. soldiers since protests erupted a week ago over the burning of Korans at an American base, according to The New York Times.

The early morning attack at a base in southern Kandahar province brings to six the number of U.S. service members killed by Afghan colleagues in the past eight days.

The shooting comes after President Obama on Wednesday defended his apology last week to Afghan President Hamid Karzai over the burning incident, saying that the apology was made to "save lives" and that it "calmed things down."