KIRKUK: A series of attacks against police in the disputed northern Iraqi city of Kirkuk on Thursday killed at least 25 people and wounded 79 others, the worst violence to hit the country in two weeks.

The attacks in the oil-rich ethnically-mixed city come with just months to go before US forces, who participate in confidence-building tripartite patrols and checkpoints with central government forces and Kurdish security officers in Kirkuk and across north Iraq, must withdraw from the country.

Three explosions - two car bombs and a magnetic ‘sticky bomb’ attached to a car - occurred around one hour apart in the oil-rich ethnically-divided city, security officials said.

The first of the blasts occurred at 9:20 am when the ‘sticky bomb’ exploded in the parking lot of the city's police headquarters, Major Salam Zangan said.

When police and emergency responders arrived at the scene shortly afterwards, a car bomb detonated.

“The explosions today killed 25 people and wounded 79 others,” said Sadiq Omar Rasul, the director of Kirkuk's provincial health department. “The majority of the casualties were police.” Earlier, Zangan had put the toll at 18 dead and 70 wounded in two initial blasts, with a security official adding 14 others were wounded in a third car bomb.

The twin blasts caused massive damage to nearby police and civilian vehicles, and several police cars with loudspeakers affixed to them could be heard appealing to Kirkuk residents to make their way to the city's hospital to donate much-needed blood for victims, an AFP journalist said.

At around 10:30 am, another car bomb exploded near the convoy of a senior police official in Kirkuk, Colonel Aras Mohammed.

He and 13 of his bodyguards were wounded in the blast, which also caused serious damage to several nearby cars and buildings, a security official said, on condition of anonymity.

Kirkuk lies at the centre of a tract of disputed territory that is claimed by both Iraq's central government in Baghdad and Kurdish regional authorities in Arbil.

US officials have persistently said that the unresolved row is one of the biggest threats to Iraq's future stability.

Thursday's death toll was the highest in Iraq since March 29, when a band of Al-Qaeda gunmen and suicide bombers managed to storm a provincial council building in the central city of Tikrit killing 58 people.

Violence is down dramatically in Iraq from its peak, but attacks remain common. A total of 211 Iraqis were killed in violence in April, according to official figures.