Three Iraqi soldiers were killed and another wounded on Saturday when unidentified attackers fired six mortar rounds at an Iraqi army post east of Dhuluiya.
Another soldier died when assailants ambushed an army patrol in al-Tharthar district, 9km west of Samarra, Captain Saad Amjad said.
Police Lieutenant-Colonel Faris Mahdi said assailants using automatic weapons killed a truck driver in a Turkish convoy ferrying food to US troops near al-Sharqat, some 330km north of capital Baghdad.
The nationality of the driver was not immediately known.
The spate of attacks came amid a claim by the Islamist group Ansar al-Sunna that it has killed 15 members of the Iraqi army.
"After having announced the kidnapping of 15 Iraqi apostate soldiers in the region of Hiyt, and after their interrogation, they confessed to the crimes they committed with the crusader forces against civilians and against the mujahidin," a statement put on the internet said.
"They were executed with bullets so that they serve as an example," added the statement, whose authenticity could not be verified.
The Army of Ansar al-Sunna has
owned up to many slayings
On 15 January, the group claimed in an internet statement that it had seized the 15 Iraqi national guardsmen west of Baghdad.
Iraq police had said 15 Iraqi soldiers were seized by armed men after finishing work at a US military base in the western province of al-Anbar.
The men, who ride daily out of the al-Asad airbase, about 150km from Baghdad, were ambushed with rocket-propelled grenades and Russian-made machine guns, police Colonel Fadil Abd al-Dulaimi said.
The Army of Ansar al-Sunna has claimed several attacks in Iraq, including the August execution of 12 Nepalese labourers and the killing of 11 Iraqi national guardsmen.
Meanwhile, Baghdad's airport will be closed on 29 and 30 January as a security measure to help safeguard the country's elections, interim Iraqi Interior Minister Falah al-Naqib said on Saturday.
He said extended night-time curfews would also be in place
throughout Iraq during the election period.