A police officer said the explosives-laden car was parked near an outdoor fruit and vegetable market.
He said six civilians and two policemen were killed, while at least 15 other people were wounded.
A medical official confirmed the casualty figures.
No one immediately claimed the attack, but it bore the hallmarks of Islamic State, which has carried out a string of bombings in the Iraqi capital over the past week, killing nearly 100 people.
