A series of bomb attacks targeting the homes of police officers injured nine and killed four people, including two children, on 4 January.
The six roadside bombs were planted in Baqouba, a former Al-Qaida stronghold, 60 kilometres northeast of Baghdad.
The attack comes during a period of political instability, where the fragile balance of power is near collapse after Shia Prime Minister Nouri Al-Maliki issued an arrest warrant for Sunni vice-president Tareq Al-Hashemi who has fled to the Kurdistan Region. The Sunni-backed Iraqiya bloc is boycotting parliamentary sessions and cabinet meetings as a result.
Officials have warned of a resurgence of Sunni and Shia militia and a possible civil war, which is looking more likely now that US troops have left the country.