Meanwhile, three hostages were freed -- two Turkish contract workers whose employer agreed to stop doing business with the U.S. military in Iraq, and a Pakistani driver, according to officials in Islamabad.
In one of Friday's strikes, insurgents used the back of a van parked next to central Baghdad's Firdous Square to fire rockets from a multiple-rocket launcher, a U.S. soldier told the Associated Press.
Another soldier said the launcher fell over as a third round was fired, setting the vehicle ablaze.
One rocket struck the Sheraton Hotel, causing minor damage, and another exploded in the parking lot of the Baghdad Hotel, used by Western security contractors.
The U.S. military said the insurgents were aiming for the "Green Zone," the heavily guarded area across the Tigris River that houses the U.S. Embassy and offices of Iraq's newly sovereign interim government.
In another attack in central Baghdad, insurgents fired rockets near the Marjam Hotel, which is used by Westerners. One rocket struck a statue in nearby Wathik Square and another landed near the Indonesian Embassy without exploding, police said, the AP reported.
In a third attack in western Baghdad, the U.S. military said a rocket hit the front gate of the fundamentalist Iraqi Islamic Party headquarters, blowing out windows and wounding a guard.
A former Coalition Provisional Authority official, speaking on condition of anonymity, said American officials believe the insurgency is being carried out by about 4,000 to 5,000 Saddam loyalists, according to the AP.
Saddam, who was arraigned in court Thursday, faces charges for his reported involvement in seven crimes committed over three decades, including invading Kuwait in 1990 and the killing of religious and political figures.
Meanwhile, the U.S. Army has charged four soldiers from the 4th Infantry Division, three of them with manslaughter, over the drowning of an Iraqi prisoner, officials said Friday, Reuters reported.
The soldiers were accused of forcing two Iraqis who had broken a curfew to jump off a bridge in the city of Samarra, north of Baghdad, on Jan. 3. One of the Iraqis made it to shore but the other drowned, according to published reports.