Officials in Iraq are investigating a suicide bombing that left at least seven dead and 12 wounded.

Charred wreckage is all that remains after police say an explosive-laden vehicle rammed into a checkpoint west of Kirkuk.

The city lies on the front line of a dispute between the Shi'ite-led central government in Baghdad and ethnic Kurds.

The Kurds want the city to be incorporated into their autonomous region in the north of the country.

No one has immediately claimed responsibility for the attack.