Protests continue for the fourth straight day in Afghanistan over the burning of copies of the Koran by U.S. troops. Hundreds of protesters have marched on the palace of Afghan President Hamid Karzai in Kabul. At least 12 Afghans have died in the protests so far. Two U.S. troops were also killed on Thursday when an Afghan soldier opened fire at a NATO base that had come under protest. Also Thursday, President Obama sent a letter to Karzai apologizing for the burning.