UNITED NATIONS (AP) - With violence in Iraq returning to pre-election levels, the U.N. secretary-general warned the Iraqi leadership and American military Thursday to take care not to step on the civil liberties of an increasingly frustrated population while fighting to crush the revitalized insurgency. Kofi Annan also said in his report that the scale and sophistication of insurgent attacks were increasing, worrying signs as Iraq's new leaders prepare to take power. Earlier Thursday, a suicide bombing at a Shiite mosque killed at least 47 people, and on Feb. 28, a suicide car bomber killed 125 people, mostly Shiite police...