In the latest bloodshed, three teachers from a college teaching oil technology died in a roadside bombing north of the oil refinery town of Baiji, police said.
A married couple and their daughter were hit by a bomb blast that targeted an Iraqi military convoy near Baiji, police added. The mother and daughter were killed. The husband was seriously wounded.
Four other people were killed in a firefight also in Baiji, police said.
Meanwhile a polling station, a government building and a police station were dynamited around the country on Sunday.
Challenges in Baiji
Major-General John Batiste, the commanding US general in the Salah-al-Din province, which is considered a potential trouble zone on election day, has identified Baiji as one of his greater
Attacks continue across Iraq
despite increased security
South of Baghdad, a polling station near Hilla was dynamited, police said.
Attackers blew up a school used as a voting centre in the town of Albu Alwan, said policeman Muhammad al-Ghanim.
No one was inside when the building was levelled, he said.
A poster on a street in Al-Dawr supposedly signed by Abu Musab al-Zarqawi's group, al-Qaida in the Land of the Two Rivers, claimed to have blown up the town's local council building on Saturday.
"The resistance has destroyed one of the lairs of the spies and collaborators. May the world be warned that he who gives his hand to the occupier and apostate will be punished," the poster read.
The statement also said the group was responsible for firing 10 mortars at a joint US-Iraqi security centre, but police said no one was hurt in the attack.
Meanwhile, a police station in the western town of Hiyt was blown up according to Iraqi officials. US marines were surrounding the town, demanding the assailants be handed over, residents said.
In the northern city of Mosul, US forces said they had detained 42 people as they battled to subdue the out-of-control city, where 20 US soldiers have been killed since 21 December, including 14 in a human bombing on a military base.
During the stepped-up patrols on Saturday in Mosul, a US soldier died in a firefight, the military said.