The Sunni and Shia leaders, escorted by army officers, were going to meet people in the local market as part of a national reconciliation campaign when they came under attack.
An interior ministry official said 46 people had been injured.
The official said the bomber rammed the vehicle into the group as they emerged from the town hall.
The private Al-Baghdadia channel said it lost a correspondent and a cameraman in the blast at Abu Ghraib, 25 km from the capital.
The suicide bomber targeted a tour of the tribal leaders under the command of Major General Mared Abdel Hassen and other officers.
Gen Hassen, who is in charge of tribal affairs in the interior ministry, escaped unhurt.
In northern Iraq, two people were killed and six injured in a car bombing in a Christian village, while a policeman was killed and another injured by a roadside bomb near the oil city of Kirkuk.
