An Iraqi military commander said the soldiers were travelling from their jobs guarding oil pipelines when they were attacked on Wednesday between the villages of Azab and Zaraqiya, 85km west of Kirkuk.
Kirkuk's deputy mayor Ismail al-Hadidi said funerals would be held on Thursday for the men "who were protecting Iraq's riches from the terrorists".
The deadliest single attack since Sunday's election, the ambush served as grim reminder to Iraq's fragile security situation.
On Tuesday, two Iraqi policemen and a soldier were killed in two attacks in the city of Baquba.
Local police said the two policemen were killed in a drive-by shooting while shopping, and died instantly.
The soldier was killed near a city hospital some 60km from capital Baghdad.
Aljazeera also learned that four Iraqis working with US troops were killed and a fifth wounded in Abu Ghraib district, west of Baghdad.
Fierce clashes between armed men and US troops were also reported in the centre of Qayim city. US positions near the customs building in the western Iraqi city reportedly came under heavy mortar attack.
The attacks come as the influential Association of Muslim Scholars (AMS) said Sunday's elections lacked legitimacy and that the national assembly and the interim government stemming out of it would lack legitimacy too.
In a statement broadcast on Aljazeera, the AMS cautioned the UN and the international community not to lose sight of the pitfalls of "legitimising such an election".
"This will open the door of evil and those legitimising the elections would be responsible," the statement said.