Colonel Muayad Bashar was travelling to work with two sergeants on Tuesday when their car hit a roadside bomb at about 7:40am (0340 GMT) close to the Abu Jafaar al-Mansur square, west of the city centre, according to Umar Muayad, second lieutenant at the al-Mamun police station.
A doctor at the Yarmuk hospital said the colonel died of his wounds shortly after he was taken to hospital.
A separate roadside bomb exploded in central Baghdad soon after dawn, but there were no casualties, witnesses said.
Fighters frequently attack Iraq's fledgling security forces, accusing them of collaborating with about 160,000 occupation troops in the country.
A car bomb against police recruits on 28 June in the city of Baquba, northeast of the capital, killed 70 and wounded 56.
US marine killed
In al-Anbar province in western Iraq, a US marine has died of his wounds received in action, the occupation military said.
According to a US military statement, the marine, assigned to 1st Marine Expeditionary force, died of wounds received in action on Tuesday while conducting "security and stability operations". No further details were provided.
Al-Anbar province is home to the towns of Ramadi and Falluja where recent US air strikes have resulted in innumerable civilian casualties.