Two explosions struck the northern Iraqi city of Kirkuk, killing at least five people and wounding more than 20 others, local medics said.

The suicide attack targeted offices of Popular Mobilisation Forces (PMF) on Atlas Street, located in the heart of the city, on Sunday, according to local media reports.

The PMF are Iranian-backed, Shia-dominated paramilitaries who have fought alongside Iraqi government forces since 2014.

The attack was the first of its kind since the Iraqi central government regained control of the multi-ethnic city last month from Kurdish Peshmerga forces - who had been in control of the area for three years.

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A controversial September 25 referendum on Kurdish secession led to mounting tensions between the Kurdistan Regional Government (KRG) and the Iraqi central government. Baghdad had declared the results of the referendum illegal.

The non-binding vote led to a military confrontation between Peshmerga forces and Iraqi government forces in Kirkuk, which was previously considered among the disputed areas of the northern region.

Kirkuk was among territory seized by Peshmerga forces when the Iraqi military abandoned the city in the face of Islamic State of Iraq and the Levant (ISIL, also known as ISIS) advances in 2014, but it is not within the borders of the KRG's autonomous territory.

There was no immediate claim of responsibility for Sunday's attack.

Baghdad has reiterated it would re-assert federal control over all borders the KRG currently controls - with Syria, Turkey, and Iran - in line with the Iraqi constitution.