KIRKUK (AFP) -- A suicide bomber killed nine Kurdish police in northern Iraq on Sunday, a district official and a  doctor said.

The bomber detonated an explosives-rigged vehicle near a three-vehicle police convoy in the town of Tuz Khurmatu, also wounding nine officers, district official Shalal Abdul Baban told AFP.

A doctor and police confirmed the toll.

The town is part of a swathe of northern territory that Kurds want to incorporate into their three-province autonomous region over the strong objections of the federal government in Baghdad -- a dispute that diplomats say is one of the main threats to the country's long-term stability.

With the latest unrest, more than 730 people have been killed in Iraq in July, making it the deadliest month in a year marked by spiralling violence that authorities have failed to stem.