Two police officers said the blast struck a bus and taxi stop around rush hour in the eastern Sadr City neighbourhood. Among the five killed was a 7-year old child. The attack also wounded 19 people, the officers added.
A medical official in a nearby hospital confirmed the causality figures. All officials spoke on condition of anonymity because they are not authorized to talk to the media.
The attack followed a wave of bombings yesterday that struck in mainly in Shiite neighbourhoods, killing 33 people.
The spike in violence comes amid growing tension between the Shiite-led government and Iraq's Sunni minority over what they consider second-class treatment. A bloody government crackdown on militants last month in a protest camp in the country's north fuelled the tension.
No one immediately claimed responsibility for yesterday's and today's attacks, but car and suicide bombings are a hallmark of al-Qaida's Iraq branch.
The spike in attacks, after a general decrease in violence, has raised fears of a return to the sectarian bloodshed that pushed the country to the brink of civil war in 2006-2007. Shiite militias have so far been largely restrained in their reactions to such bombings.