Three Iraqi soldiers were killed in a bomb attack on their convoy in the city of Samarra on Tuesday. The city was recaptured by US forces after a major assault in October.
Further south, three national guardsmen were killed in a roadside bombing near the town of Baquba.
A Turkish truck driver was also killed in an ambush in the same area, police said, adding that he was working under contract with the US military.
In the nearby town of Duluiya, a fighter was killed and five soldiers wounded in a firefight, police said.
Meanwhile four US soldiers have also been killed in roadside bombings. A single blast in the Iraqi capital claimed three soldiers, while a bomb in the town of Balad north of Baghdad claimed a fourth.
Earlier on Tuesday, two shells landed in the grounds of a Baghdad mosque where Sunni Muslim clerics and politicians were meeting to discuss the 30 January elections they want postponed, but no one was hurt.
They said one shell exploded near Umm al-Qura Mosque, the headquarters of the influential Association of Muslim Scholars - which has called on Iraqis to boycott the poll because of US-led attacks on Sunni areas.