The attackers first fired mortar rounds at a nearby military base and bombed a communication tower to draw security forces' attention away before intercepting the convoy last night near Sarha village, said Col. Hussein Ali Rasheed.
The village is located just outside the northern city of Tuz Khormato, about 200 kilometres (125 miles) north of Baghdad.
According to Rasheed, the city's police chief, all the casualties were Shiite truck drivers from Baghdad and their assistants. Their bodies were found with gunshots to the head, he said.
Across Iraq, insurgents have in the recent months escalated attacks on civilians and government forces. The violence has reached levels not seen since 2008, fuelling worries of a return to the widespread sectarian killing that pushed the country to the brink of civil war after the 2003 US led invasion. More than 3,000 people have been killed since April.
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Insurgent attacks have also become more audacious, such as Sunday's raids against two major high-security prisons near Baghdad that killed dozens and set free hundreds of inmates, including al-Qaida-linked militants.
Many of the escaped prisoners were senior members of al-Qaida in Iraq, including some who were facing the death penalty, according to Interpol.