While the predominantly Shiite south has been plagued by fighting between rival militias, massive blasts such this are quite rare. The last such bombing was in November 2003 when a suicide truck bomber attacked the headquarters of Italian forces stationed there, killing more than 30 people. The blast, which is the signature attack of al-Qaida in Iraq, is the latest in a series of high-profile explosions that have raised concerns about a resurgence of violence as the U.S. military faces a June 30 deadline to withdraw from urban areas in Iraq. The explosives-laden car detonated at 9 a.m. in the center of the commercial area, according to police, in the town of...