Two government employees were killed in a Baghdad drive-by shooting on Wednesday while an Iraqi translator working for the US military was slain north of the capital.
The killings are the latest in a string of attacks against Iraqis seen to be supporting the US-backed Iraqi government and American-led troops.
Security officials said two carloads of armed men fired on a vehicle carrying Industry Ministry officials Zaki Jawad and Muhammed Haider, killing both.
Fighters also killed Mustafa Ashraf, a translator working for US troops, as he was driving between the towns of Khalis and Baquba, 60km northeast of Baghdad.
Also in Baquba, a car bomb exploded at 10.15am (0615 GMT) near a petrol station where cars were waiting for fuel, killing two civilians and destroying five vehicles.
Three US soldiers were killed in two attacks in Iraq late on Tuesday.
Some 1679 US troops have been
killed since the invasion of Iraq
The US military said in a statement on Wednesday that a mortar attack on a base at Tikrit killed two soldiers of the 42nd Infantry Division.
A soldier from the 1st Corps Support Command was killed when a roadside bomb blasted his vehicle just north of Baghdad, the statement added.
The deaths take to 1679 the number of US troops killed since the March 2003 invasion and to more than 870 people in total, including US military personnel, since Iraq's new government was announced on 28 April.
Meanwhile, Iraqi soldiers backed by US forces continued their military operation in the northern town of Tal Afar in search of what they called terrorists.
An Iraqi journalist in the town told Aljazeera that hundreds of people were arrested in the operation.
Nasir Ali said the arrested were civilians who had no links with any group and denied the existence of foreign fighters in the town as claimed by the US forces.
He added that the arrests were based on false information and were concentrated on certain areas in the town.
In another development, a main oil pipeline in northern Iraq was blown up early on Wednesday.
The line was used to export oil to
An official at the Northern Oil company said the line affected was used to export oil to Turkey from Iraq's vast northern oil fields around Kirkuk.
The company official said there had been no exports at the time because of repeated attacks.
"This isn't the first time. They've targeted oil for a long time even when there is no exporting," he said on condition of anonymity.
Iraq says 95% of its national income comes from crude oil exports and says it aims to lessen its dependency on them.