The journalists, a Pole and an Algerian, were shot in their car by gunmen in a passing vehicle near Mahmoudiyah, about 20 miles south of Baghdad, said police Lt. Alaa Hussein. A second Pole was wounded in the attack.
An American missionary and two CNN employees were killed in February and January in the same area.
In Karbala, U.S. troops skirmished with militiamen loyal to anti-U.S. cleric Muqtada al-Sadr, witnesses said. The exchange began when a roadside bomb hit a U.S. patrol, damaging three vehicles, prompting a clash between gunmen and troops, the witnesses said.
Al-Sadr's al-Mahdi Army militia was out in force in Kufa and Najaf on Friday, fearing a U.S. assault to capture al-Sadr could be imminent. Militiamen and U.S. troops had a fierce mortar exchange overnight.
Fighters — draped with ammunition belts and carrying automatic weapons and rocket-propelled grenade launchers — moved around the streets of the two cities in large numbers and took positions behind earthen mounds and behind buildings.
"We will fight until the last drop of our blood," said one fighter, Dhia Shami, behind a dirt barricade.
In other developments:
In a sign of continued problems with the tracking of contracts, Pentagon officials on Thursday acknowledged they have yet to identify which Army entity manages the multimillion-dollar contract for interrogators like the one accused in the Iraq prisoner abuse probe.
Rumsfeld also acknowledged his department hasn't completed rules to govern the 20,000 or so private security guards watching over U.S. officials, installations and private workers in Iraq.
Every Friday for the past three weeks, al-Sadr has traveled from Najaf to deliver the prayer sermon at the main mosque in Kufa — moving freely despite the hundreds of U.S. troops deployed outside Najaf on a mission to capture the renegade cleric.
Al-Sadr arrived at the Kufa mosque surrounded by gunmen and followers. Supporters chanted "No one can beat al-Sadr" as his car pulled up at the mosque and he quickly slipped inside.
U.S commanders suggested they would stick to their policy of not moving against him on Fridays out of respect for the weekly Islamic day of prayer.
U.S. troops have been trading very carefully in their confrontation with al-Sadr, whose militiamen control the three holiest Shiite cities in Iraq. While vowing to capture him, the military has also said it will not approach holy shrines, fearing that any damage to the sites would outrage Iraq's Shiite majority.
Still, clashes between U.S. troops and al-Mahdi Army have intensified the past week. A barrage of mortars hit the U.S. base in Najaf, the latest in near nightly shelling that so far has caused no U.S. casualties. The U.S. troops responded with heavy force, firing back with mortars and howitzers, while F-16s overhead directed fire.
The militiamen's mortar position was destroyed, said Maj. Todd Walsh, of the 2nd battalion, 37th regiment, 1st Armored Division. With each night's fire, the fighters' mortars had become more accurate as they honed in on the base, so commanders decided to intensify their response to wipe out the position, Walsh said.
On Thursday, U.S. troops seized the two-story governor's office in Najaf, after drawing militants away from the city center with a gunbattle outside the city that the Americans estimated killed some 40 militiamen.
Later, a U.S. convoy of Humvees leaving the Najaf area was ambushed twice in 10 minutes by insurgents firing rocket-propelled grenades and automatic rifles from rooftops. An AP reporter saw five militants apparently hit by U.S. retaliatory fire.
Coalition troops also clashed with dozens of al-Sadr militiamen in Karbala, 50 miles north of Najaf, on Thursday night.
A witness told Associated Press Television News that troops fired on the insurgents and destroyed four buses of Pakistani pilgrims, which were seen burning. The witness said "three or four" Pakistanis were killed.
In the past two days, U.S. soldiers estimate they have killed about 80 militiamen. One U.S. soldier was killed Wednesday.
The fighting came as chief U.S. administrator L. Paul Bremer announced the appointment of Adnan al-Zurufi as governor of Najaf province — part of the campaign to wrest control from al-Sadr's militiamen.
The United States plans to hand some sovereignty to a transitional Iraqi government June 30 and is looking to end al-Sadr's uprising, which has left parts of southern Iraq outside coalition control.