The roadside bombing killed two civilians at a popular market in central Baghdad's Rusafi Square neighbourhood, security officials told AFP.

Insurgents often target markets in Baghdad in a bid to inflict maximum casualties as US and Iraqi forces try to rein in the violence with an ongoing security clampdown in the capital.

Four more people were reported killed northeast of Baghdad in the restive province of Diyala.

Two people, including a schoolchild, were killed when gunmen sprayed their minibus with bullets in Al-Aswad near the town of Khalis, police Lieutenant Ahmed Ali said from the provincial capital of Baquba.

In a similar incident, gunmen shot dead two more people in the village of Albu Aziz, east of Baquba, he added.

Attacks in Diyala have risen since the military crackdown in Baghdad as Iraqi insurgents seek easier targets in neighbouring provinces.