The attacks underscore the fragility of Iraq’s security since U.S. combat troops withdrew from urban areas on June 30 and as the country prepares for elections in January. The withdrawal from cities is part of a U.S.-Iraqi agreement signed in January that outlines the complete pullout of American forces by the end of 2011. Oil prices and energy stocks rallied after the U.S. Department of Energy said that U.S. crude-oil inventories plunged unexpectedly last week by 8.4 million barrels. Crude for September delivery gained $3.23 a barrel, or 4.67%, to settle at $72.42. Oil has climbed more than 8% in two days and is at its highest level since June 11.