Protests in Pittsburgh are getting into full swing as Barack Obama and other world leaders arrive for the G-20 summit. Police fired pepper spray and smoke bombs to break up an unauthorized march of about 500 anarchists heading toward downtown, reports the Post-Gazette. Its live blog of the march says some protesters threw rocks at police, and at least one person was arrested. The G-20 summit gets under way tonight and wraps up tomorrow. (More Pittsburgh stories.)