He was part of a military convoy which came under fire at al Mussayih, 40 kilometres north of Karbala.
The dead man was a 44-year-old commander with the Polish Army, which now commands a 9000-strong multinational occupation force patrolling a large sector of central and southern Iraq.
Two American soldiers also died in separate incidents near Baghdad and along the Syrian border, as attacks took place throughout the occupied country.
One soldier was killed early on Thursday when his truck hit a landmine near the Husaybah border crossing point with Syria about 315km northwest of Baghdad, according to US military officials.
A paratrooper was also killed and two others wounded when their patrol came under rocket-propelled grenade (RPG) attack near Mahmudiya, 25km south of Baghdad late on Wednesday, announced the military.
Their deaths bring to 140 the number of US soldiers killed in Iraq by hostile fire since US President George Bush declared an end to major combat on 1 May.
A total of 114 US soldiers were killed in the active combat phase which began on 20 March.
First Polish casualty
And a Polish major was seriously wounded in an ambush south of the capital near Karbala on Thursday, as he was returning from a promotion ceremony for the Iraqi civil defence corps, according to Polish officials.
It is the first casualty suffered by Warsaw’s troops in Iraq.
In the north, an Iraqi interpreter working with US forces was also injured when assailants fired at a checkpoint manned by occupation soldiers and Iraqi police.
Polish (front row) and US soldiers
during a handover ceremony
Occupation officials did not immediately confirm the incident.
The latest attacks coincide with as a senior Japanese official's saying his country would stand by its commitment to send forces to Iraq despite the heightened threat to Japanese military and civilian personnel.
Meanwhile, Iraqi judges investigating alleged atrocities by former Iraqi President Saddam Hussein's government are angry with US-led occupation forces for failing to provide more protection as their colleagues fall victim to assassins' bullets.
“We risk our lives every day. The Americans only talk,” said one prominent judge who asked not to be named.
“We are losing colleagues. Seven months have already passed since the fall of the Saddam Hussein regime, and the Americans still have not fulfilled their promises to give us protection,” he said.
Anger is running particularly high in the city of Najaf, where the governor called a strike by municipal staff after a meeting with occupation officials on Wednesday failed to secure pledges to improve security, following the latest assassination to target the judiciary.
Muhan Jabr al-Shuwaili, the top judge in Najaf, was murdered on Monday by unknown assailants who told him "Saddam has ordered your prosecution" before shooting him dead.
In other news, Democratic presidential contender Wesley Clark said the United States should resist pressure for an early exit in Iraq.
Clark, in a speech designed to clarify his positions on domestic and foreign policy, said Washington should appoint an allied high representative to guide Iraq's reconstruction while shifting the military operation to NATO forces under US command.
"Early exit means retreat or defeat. There can be neither," he said. "First we must end the American monopoly on the occupation and reconstruction. Then we must develop the right force mix to fight and win guerrilla war."