Mohammad Rashad, a lieutenant-colonel with the country's special oil protection force, was shot dead on Tuesday by armed men in front of his house in oil-rich Kirkuk in northern Iraq.
His bodyguard was also killed, police said.
Armed men also shot dead Major Diya Hilal Taha, chief of Al-Ghazalia police station in western Baghdad when they opened fire on his patrol. His three bodyguards were wounded.
One policeman was killed and four others wounded when a car bomber blew himself up next to a police checkpoint close to al-Tharthar police station west of Samarra.
A mortar fell on a house in the village of Albuahil east of Tikrit, ousted president Saddam Hussein's hometown, killing one and wounding another.
Rebels have been carrying out sustained attacks on Iraq's fledgling security forces in recent months.