BAGHDAD, Iraq - A huge explosion shook the center of Iraq (news - web sites)'s capital before dawn Saturday, hours after the most ferocious attack of the war left Saddam Hussein (news - web sites)'s Old Palace in flames and Baghdad shrouded in smoke. Aircraft could be heard overhead, but it was unclear what had been targeted. Following the single blast, sirens presumably from ambulances or police cars could be heard racing through the city. The blast at first light shattered the eerie silence that had fallen over Baghdad after the rain of missiles Friday evening. The barrage, which began...