The BBC's Paul Wood and Rageh Omaar in Baghdad have been witnessing massive air strikes as the US unleashes what it calls its "shock and awe" strategy.
Their movements are restricted by the Iraqi authorities.
"Wave after wave of missiles have struck all over the city. The attacks are much worse than the previous two nights.
Flashes lit up the night sky and plumes of flame and ash shot hundreds of feet into the air transforming the heart of the city.
The thud of detonation as government buildings and presidential palaces were hit was audible from all parts of the city.
Volleys of tracer fire light up the sky, powerless to interrupt the bombardment.
And across the horizon of the capital, flames are licking around familiar landmarks.
There has been a brief lull between the waves of attack.
Air raid sirens have wailed, but few people needed any warning - they have been taking shelter all day.
Even in the calm of daytime, normally bustling markets are deserted as families do not dare to leave their homes."
"Baghdad's defenders tried futilely to knock down incoming missiles and aircraft which were anyway flying high above the range of the guns.
But there was very little anti-aircraft fire by the time the second wave arrived.
We heard the sound of aircraft flying quite low over the city then.
One eyewitness in the Iraqi capital said there were now hundreds of armed men frantically digging trenches and making defensive positions on the outskirts of the capital."