The Associated Press news agency said that a policeman was among the dead, but that report could not be immediately verified.
'Awakening' leader killed
Elsewhere in Iraq on Tuesday, gunmen killed the leader of a government-backed armed group outside his home in the village of Jurf al-Sakhr.
Malik Yaseen was killed and two of his bodyguards wounded in a drive-by shooting, the AFP news agency said.
Yaseen had been the leader of a Sunni "Sahwa" or "Awakening" armed group, one of many across the country that have been supported and funded by the Iraqi government and US forces.
Two other explosions also struck the Iraqi capital, both involving bombs attached to vehicles.
Each attack left two people wounded, Reuters said.