More than 40 cruise missiles have been fired at Baghdad since the United States began military strikes against Iraq earlier Wednesday night, CNN reported.
F117A stealth bombers were reportedly involved in the strikes, with each carrying two cruise missiles.
A US-led large scale military operation against Iraq is expected more than 12 hours away, CNN said.
US defense officials said the early strikes are limited in scale and aimed at preparing the battlefield for a massive attack.
US warplanes started raiding Baghdad about one and a half hoursafter the expiry of the deadline set by US President George W. Bush for Iraqi President Saddam Hussein to leave Iraq or face war.
The first round of air raids started at 0530 a.m. (0230 GMT) Thursday and lasted for about 20 minutes. Tracer fire and a large ball of smoke was seen in the south of the city. After a brief interval, US warplanes resumed air attacks.
Buildings of the Iraqi leadership were attacked in the three rounds of US air raids on Baghdad, leaving several casualties.
Iraqi anti-aircraft forces fired back at the US warplanes, witnesses said.
The war was declared after the United States, Britain and Spainfailed to win support of majority in the UN Security Council for their draft resolution that would have authorized a war on Iraq.
Three permanent members of the Security Council, namely France,Russian and China, opposed the US-led military attack on Iraq and insist that inspections should continue.
More than 250,000 US troops in and around the Gulf region, joined by about 45,000 British troops, are launching military strikes on Iraq.