Gunmen attacked two foreign exchange shops in the central Iraqi city of Baquba on Saturday, killing six people and stealing money before setting off a car bomb when police arrived, officials said.
The attack occurred at around 12.40pm (0940 GMT) in the centre of the city, 60 kilometres north of Baghdad, a security official in the provincial security command said, speaking on condition of anonymity.
The gunmen shot dead three people in each currency exchange store before stealing an unspecified amount of money and fleeing the scene.
When police arrived at the looted shops, a car bomb exploded nearby, wounding four civilians and five policemen, including Colonel Mudhafar al-Mujamaie.
It was not immediately clear who was behind the attack.
Iraqi officials have accused insurgent groups like Al-Qaeda of robbing banks, currency exchange shops and jewellery stores in a bid to fund their activities.
Diyala province, of which Baquba is the capital, remains one of Iraq's most violent, despite numbers of attacks having fallen nationwide since their peak in 2006 and 2007.