Police officials say the bomber rammed his explosive-laden car into the checkpoint in Baghdad's northern district of Shulla this afternoon, killing three policemen and three civilians.
The officials say that at least 15 people were wounded and several cars were burned in the attack.
Medical officials in nearby hospitals confirmed the casualties. All officials spoke on condition of anonymity because they were not authorised to speak to the media.
Nobody immediately claimed responsibility for the attacks. Baghdad and outlying areas see near-daily bombings.