Authorities imposed a curfew Monday on parts of Iraq's Kirkuk amid fears of unrest as the ethnically mixed city took part in an independence referendum organised by the country's Kurds.

"A total curfew has been imposed until further notice" in the city centre and in Arab and Turkmen areas "to ensure security, monitor the situation and protect the citizens of Kirkuk," police Colonel Afrasiyao Kader told AFP.

An AFP photographer saw security force members affiliated to the Iraqi interior ministry on the streets of the city soon after the announcement was made.

Voting took place in the oil-rich Kirkuk province despite it not forming part of the three-province Kurdish autonomous region in northern Iraq.

According to a police source, the curfew was decided to prevent incidents between the Kurdish, Turkmen and Arab communities which share the city.

It was not enforced in Kurdish districts of Kirkuk where voting was extended until 7:00 pm (1600 GMT) as for Iraqi Kurdistan.

Enthusiastic voters turned out in large numbers in mainly Kurdish areas, waving the national flag to the sounds of ethnic music, in contrast to quiet streets in Turkmen and Arab districts.

The non-Arab Kurds say that historically Kirkuk belongs to them, arguing that the late dictator Saddam Hussein chased them out and replaced them with Arabs.

Kirkuk governor Najm Eddine Karim, a Kurd, was fired by authorities in Baghdad last week after his provincial council decided to take part in the poll but has refused to vacate the post.