Amidst the offensive, two more US soldiers were killed and three wounded in a resistance attack near Samara, north of Baghdad on Thursday.
A spokesman for the 1st Armoured Division said US forces hit five targets around Baghdad with mortar fire on Friday evening in the third successive night of "Operation Iron Hammer", the drive to attack resistance positions.
Witnesses reported several explosions around the airport, in the southwest of the city, as US planes and helicopters flew overhead.
Near the Syrian border, 82nd Airborne sources said F-16 fighter jets on Thursday night destroyed an isolated three-story building. They claimed it was a staging area for attacks and storage of ammunition.
Fearing a al-Nasiriya-type attack which killed at least 18 Italian military personnel, the US-led occupation administration shut its headquarters in the southern city of Basra for 36 hours for a security review.
US soldiers, sitting targets for
The US offensive follows extensive resistance attacks on the headquarters of the occupation administration in Baghdad in recent days in which dozens of American soldiers have been killed.
US casualties occurred on Thursday in a bomb attack near the city of Samara, 110 km north of Baghdad close to the hometown of former president Saddam Hussein, the US military said.
The soldiers' deaths raised to 159 the number of US troops killed in combat in Iraq since 1 May, when US President George Bush declared major combat over.
Earlier, a US helicopter gunship killed seven people allegedly preparing to launch rocket attacks on an American military base in Iraq.
A US military spokeswoman said the group was spotted preparing the attack on Thursday night north of Baghdad when the Apache swung into action and attacked them.
"The AH-64 engaged the would-be attackers, killing seven, wounded one while another managed to flee," said Major Josslyn Aberle of the 4th Infantry Division.
Those killed were supposedly preparing to target the US army's Speicher base some 200km from Baghdad.
Aberle said the pre-emptive strike was part of "Operation Ivy Cyclone" launched after a Black Hawk helicopter was shot down on 7 November near Tikrit, the hometown of the Iraq's ousted ruler Saddam Hussein.
The US spokesman claimed ground troops deployed later at the scene found a truck carrying 50 missiles, a bunker containing 300 rockets and between 200 and 300 missiles.
"The AH-64 engaged the would-be attackers, killing seven, wounded one while another managed to flee"
Major Josslyn Aberle,
US military spokeswoman
She explained Operation Ivy Cyclone focused on "aggressive operations" that notably aimed to "locate and detain those forces conducting anti-coalition activities."
Meanwhile, US forces claimed to have captured four men early on Friday who are suspected of downing helicopters of the occupation forces.
"We were targeting individuals believed to be involved in the downing of US aircraft, helicopters," Lieutenant Colonel Steven Russel, who heads a battalion of the 4th Infantry Division, said.
The four were chiefly suspected of shooting down the Chinook helicopter near Falluja last week.
Sixteen US soldiers died when the Chinook crashed on being hit by a rocket.
"We were looking for four specific individuals and we found all four. We detained a few others for questioning," Russel said.