BAGHDAD — 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 police convoy in the town of Tuz Khurmatu in Salaheddin province, 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 Iraqi Kurds want to incorporate into their three-province autonomous region over the strong objections of the federal government in Baghdad.

Diplomats say the dispute is one of the main threats to Iraq's long-term stability.

Security forces, meanwhile, began a major operation on Sunday in Diyala, Salaheddin and Kirkuk provinces, aimed at tracking down those behind bombings and assassinations during the Muslim holy month of Ramadan, Lieutenant General Abdulamir al-Zaidi said.

All three provinces have been hit by frequent attacks, including in recent weeks.

In Baghdad, a magnetic "sticky bomb" on a bus killed two people and wounded eight on Sunday, while an employee of the Southern Oil Company was shot dead in Basra province in the country's south, officials said.

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