A suicide bomber detonated an explosives-rigged vehicle at a checkpoint north of Baghdad on Tuesday, wounding a senior intelligence officer and killing four police, security officials said.
The bomber attacked the convoy of Colonel Qassem al-Anbaki, the head of police intelligence in Diyala province, at a checkpoint, army and police officers said.
The blast in the Jdaidat al-Shatt area, south of Diyala capital Baquba, also killed four policemen, including a first lieutenant, and wounded nine other police, the officers said.
A doctor at Baquba General Hospital confirmed the toll.
There was no immediate claim of responsibility for the attack, but suicide bombings are a tactic frequently used by Sunni militants in Iraq, including the Islamic State jihadist group.
The attack followed two blasts, one of them a suicide bombing, that targeted a cafe north of Baquba the day before, killing 20 people.
Iraq declared victory over IS in Diyala early last year but that has not brought an end to attacks by the jihadists.
IS overran large areas north and west of Baghdad in June 2014, but Iraqi forces backed by US-led air strikes have since dealt the jihadists significant defeats.