A senior Iraq finance ministry official and his staff have been attacked as they travelled in a convoy in Baghdad.
Residents said the air strike shook the eastern side of Falluja
Head of the audit board, Ehsan Karim, was taken to hospital with injuries and two of his bodyguards were reportedly killed in the bomb blast.
Elsewhere, a US soldier was killed in an attack on a convoy in northern Iraq, and at least four people died overnight in a US strike on a house in Falluja.
Meanwhile, Lt Gen Ricardo Sanchez has stood down as top US commander in Iraq.
Mr Karim's convoy was hit at about 0800 local time (0400 GMT) in the Yarmuk district of west Baghdad.
An interior ministry official said a bomb had been attached to one of the vehicles in the convoy in which Mr Karim was travelling.
Two of his bodyguards were said to have been killed in the blast, and Mr Karim was taken to hospital with injuries.
There were unconfirmed reports that he later died of his wounds.
In the northern city of Mosul, a soldier was killed and two wounded when their convoy was attacked by a roadside bomb on Thursday, said a US military spokesman.
The spokesman did not give the nationalities of the victims.
In the first major US military strike since power was handed to the Iraqis on Monday, a suspected militants' hideout was targeted in the city of Falluja overnight.
At least four people were believed to have been killed, and 10 wounded in a blast that residents said shook the eastern end of the city.
A US military spokesman said as many as 15 were killed in the air strike and subsequent shoot-out.
Brig Gen Mark Kimmitt said they conducted a strike on a "known safe house" for members of the Tawhid and Jihad movement led by senior al-Qaeda member Abu Musab al-Zarqawi.
"We believe 10 to 15 people were killed, our first inclination is that they would be foreign fighters," he told French news agency AFP.
"We have strong intelligence to believe suicide bombers were among those killed."
US authorities accuse Zarqawi, believed to be a close ally of al-Qaeda leader Osama Bin Laden, of masterminding a series of spectacular suicide bombings in Iraq and beheading a US hostage in Iraq.
On Wednesday, US Secretary of State Colin Powell increased the reward for information leading to Zarqawi's arrest or conviction from $10m to $25m.
At a ceremony in the main military base in Iraq on Thursday, Lt Gen Ricardo Sanchez stepped down as head of US troops in the country.
He is being replaced by General George Casey, the second highest officer in the US army.
The Bush administration has denied the departure of Gen Sanchez is connected with the scandal over the abuse of Iraqi prisoners by US soldiers at Abu Ghraib.
But correspondents say an inquiry into the mistreatment at the prison near Baghdad has put his leadership under intense scrutiny.