BAGHDAD – Al-Qaida in Iraq's new leader warned Shiites on Friday that "dark days soaked with blood" lie ahead and that a new campaign of attacks was under way. Later Friday, three suicide bombers blew themselves up at a sports field in a predominantly Shiite town in northern Iraq, killing at least 10 people and wounding another 120, police and hospital officials said. Only days before the warning, Iraq was wracked by the worst attack this year, a series of coordinated bombings and assassinations that killed 119 people — most of them Shiites and members of the security forces —...