Afghan protesters burn a picture of U.S. President Barack Obama during a protest in Khost province February 24, 2012. Twelve people were killed on Friday in the bloodiest day yet in protests that have raged across Afghanistan over the desecration of copies of the Muslim holy book at a NATO military base with riot police and soldiers on high alert braced for more violence. REUTERS/Anwarullah (AFGHANISTAN - Tags: CIVIL UNREST RELIGION)