"A 1st Armoured Division soldier died from wounds received when his convoy was struck by an improvised explosive device at 8.20am (05:20 GMT) on November 14 in central Baghdad," a military statement said.
"Two other soldiers received shrapnel wounds," it said.
Earlier on Friday, the US military said two US soldiers were killed and three others wounded in a bomb attack on their convoy north of the Iraqi capital on Thursday.
The deaths have raised to 160 the number of US soldiers killed in combat in Iraq since 1 May, when US President George Bush declared major hostilities over.
Also, an American civilian working for the US army was killed and another wounded when they came under fire while travelling north of Baghdad near Balad, a military spokeswoman said.
Meanwhile, US warplanes and ground forces pounded targets in Iraq on the third day of operations against the resistance.
Near Saddam's hometown Tikrit, a US Apache helicopter spotted and killed seven Iraqi fighters late on Thursday as they prepared to fire rockets at a US military camp, a US army spokeswoman said.
A spokesman for the 1st Armored Division said US forces hit five targets around Baghdad with mortar fire on Friday evening in the third successive night of "Operation Iron Hammer", an American drive to attack guerrilla positions.
"These are locations the enemy has used to fire on us. Today we are firing first," he said.
Witnesses reported several explosions around the airport, in the southwest of the city, as US planes and helicopters flew overhead. Later in the evening, a succession of blasts echoed from northwest Baghdad.
The tougher US tactics follow Iraqi mortar and rocket attacks on the headquarters of the US-led administration in Baghdad and a bloody few weeks in Iraq in which 16 Italian soldiers and dozens of American troops have been killed.
US officials have denied Washington was in trouble, but opinion polls show declining support among US voters for the occupation as Bush seeks re-election a year from now.
"Look, we will stay until the job is done, and the job is for Iraq to be free and peaceful"
Key ally Japan has also shown cold feet about sending troops in the wake of Wednesday's bomb attack on an Italian military base that killed at least 27 people.
"Look, we will stay until the job is done, and the job is for Iraq to be free and peaceful," Bush said in response to concerns the US shift in strategy to speed up the transfer of authority to the Iraqi people could lead to a premature withdrawal of US forces and leave the country in chaos.
US officials said the initial plan had been for a transfer of sovereignty after a new Iraqi constitution was ratified and elections held but the administration was considering ways to transfer some responsibility sooner.
Raids around Saddam Hussein's hometown of Tikrit have uncovered evidence of a sophisticated Iraqi resistance under a tightly controlled chain of command, a US official said on Friday.
US Major Bryan Luke said it appeared guerrillas were moving freely from Fallujah, at the southwestern tip of the so-called Sunni Triangle, the area of most intense resistance activity, east to Baghdad and up to Tikrit, the northern point of the triangle.
He said the guerrillas operated in cells of up to 12 people, broken down into groups of four with a strict chain of command.
"I think they're moving more and coordinating their movements more precisely between those cities," said Luke, a senior officer in the 1/22 Infantry Regiment of the 4th Infantry Division.
He said there was also evidence the guerrilla cells were using satellite phones, walkie-talkies and even low-range mobile phone networks to communicate.
"In the case of the Black Hawk attack, it looks like they had spotters on the banks of the Tigris in communication with those who fired the weapon at the helicopter," Luke said of an attack earlier this month on a US helicopter.
The increasing sophistication and coordination of the Iraqi forces was noted by General John Abizaid, the head of US Central Command, in a speech in Washington on Thursday.
"Would anyone who speaks Arabic please contact me? I have to stop talking now, OK?"
Abducted reporter Carlos Raleiras' plea for help
Abizaid said Iraqi resistance forces now numbered around 5000, including Saddam loyalists, criminals paid to stage attacks, a small number of foreign fighters and some Shia guerrillas.
Underscoring Iraq's fragile security, gunmen shot and wounded a Portuguese reporter and kidnapped a second in southern Iraq on Friday after attacking a convoy of vehicles, the British military and Portuguese media said.
The kidnapped reporter, Carlos Raleiras of private radio station TSF, made a plea for help on his mobile phone.
With voices speaking in Arabic behind him, Raleiras said, "Would anyone who speaks Arabic please contact me? I have to stop talking now, OK?"
An Egyptian reporter for the French-based EuroNews TV network told Portuguese TV network SIC he had spoken with the kidnappers via mobile phone and they were demanding $50,000 for Raleiras' release. His employer TSF declined to comment.
Portugal called on US and British authorities for support in the hunt for Raleiras.
A number of foreign reporters were killed covering the war to oust Saddam Hussein and its aftermath, but this is the first known abduction of a journalist.