The council in Kirkuk, an ethnically mixed region of northern Iraq under Baghdad's control, voted Tuesday to take part in next month's Kurdish independence referendum, councillors 

The central government in Baghdad is strongly opposed to Iraqi Kurdistan's planned September 25 referendum, which is non-binding but could lead to independence

Kirkuk, an oil-rich province made up of Kurds, Arabs and Turkmen, is under Baghdad's control but is claimed by the autonomous Iraqi Kurdistan region

In Tuesday's vote, 22 of the 24 present councillors in the 41-member Kirkuk council voted in favour of holding the referendum, said councillor Hala Nur Eddine

Speaking to journalists afterwards, Kirkuk governor Najm Eddine Karim described the vote as a "historic event"

But a spokesman for Iraqi Prime Minister Haider al-Abadi denounced the vote as "illegal and unconstitutional"

"Provinces that don't belong to the autonomous region (of Kurdistan) can't impose decisions without the federal government's approval, and Kirkuk is one of these regions," said Saad al-Hadithi

The plans to hold the referendum have been criticised by neighbouring Turkey and Iran, which have large Kurdish minority populations

The Turkish foreign ministry said in a statement that the Kirkuk's council decision was "another link in a chain of mistakes" and "once more a serious violation of the Iraqi constitution."

There are also doubts about the vote among the five million Iraqi Kurds, with some calling for it to be postponed

The United States has made the same demand, saying the referendum could distract from the fight against the IS group by stoking tensions between the Kurds, and Arabs and Turkmen

The dispute over Kirkuk is seen as a reason for delays to the launch of an Iraqi-Kurdish military offensive aimed at recapturing the city of Hawija from IS group.