The three men - two journalists and a driver - were on their way back to Baghdad from the Shia holy city of Kerbala on Monday when they were ambushed near the towns of Mahmudiya and Latafiya in the lawless area known as the Triangle of Death.
Hundreds of Iraqi police and soldiers and Shia pilgrims have been killed while travelling through the area, and several foreigners have also been kidnapped or killed in the region.
Meanwhile, four Iraqi soldiers were killed and four wounded on Monday morning in an attack on an army camp in central Iraq, an army officer said.
Three were hurt when four mortar shells slammed into the camp at Khan Bani Saad, 20km south of Baquba, shortly before 9am (0500 GMT).
A patrol sent out in pursuit of the attackers was then caught in an explosion with the loss of four soldiers, while another was wounded, according to the captain who declined to be named.
In another incident, also on Monday, two civilians were killed and four others, including two soldiers, were injured when a bomb exploded while an Iraqi army convoy was driving through the Saydia district of southern Baghdad, a Defence Ministry official said.