The attack took place in Adan Square, in a predominantly Shiite part of the capital, and appeared to be the latest in a near-daily string of attacks carried out by Sunni Islamic extremists targeting the country's Shiite majority.
A police officer provided the death toll and said 45 other people were wounded. A medical official confirmed the casualty figures. Both officials spoke on condition of anonymity as they were not authorized to brief the media.
The government has struggled to impose security following the 2011 withdrawal of US forces. Last summer the Islamic State group, which has claimed several previous attacks in and around the capital, swept across a third of the country, capturing the second largest city Mosul.
A US-led coalition has been carrying out airstrikes against the extremist group since August.
