Dawn in Baghdad brought more air raid warnings and explosions, after several hours of quiet that followed massive air strikes.

Just before dawn, a huge explosion shook the center of Baghdad, ripping through the silence that had settled over the city for a period, after a night of ferocious bombing by U.S. and coalition forces.

Air raid sirens had wailed periodically through the night in Baghdad, as hundreds of bombs and missiles rained down on the capital, in the start of what military planners call a "shock and awe" air campaign. Explosions were also reported in the northern cities of Mosul and Kirkuk.

Among the targets hit was Iraqi President Saddam Hussein's Old Palace compound and military command and control facilities.

Coalition troops advancing from the south also took control of key oil facilities in southern Iraq.

Meanwhile, Iraqi forces continued to surrender, and U.S. military officials say the commander of an Iraqi army division surrendered to coalition forces advancing toward Basra in southern Iraq.

In northern Iraq, about 1,500 Turkish troops have crossed over the border.