Kirkuk on Tuesday was set to impose the curfew and tough security in a bid to ward off attacks during the country's election scheduled for 30 January.
From Tuesday, Kirkuk authorities ordered an 8pm to 5am curfew which will be extended by two hours on the eve of the election, in which Iraqis will vote for a national assembly to draw up a new constitution.
A senior police official said his forces were ready to give their lives for Sunday's vote, while the governor of Kirkuk province has been holding daily meetings with community leaders to secure their help to counter fighters opposed to the presence of foreign troops in Iraq.
"We have been preparing for three months and we will sacrifice our lives for the security of the vote," said Major Yadgar Abd Allah, who is coordinating security for the election.
Polling centres attacked
Elsewhere 10 polling centres north of Baghdad were attacked overnight, police reported. A further voting station was hit in the south of the country.
Mortar rounds and rockets pounded three voting centres in Tikrit on Monday night and a fourth station was hit on Tuesday morning, Iraqi police Colonel Abd Allah al-Juburi said.
Centres were attacked with
mortars and small arms fire
In Tuz Khurmatu, north of Tikrit, fighters dynamited a voting station, said Captain Ahmad Bayan al-Din.
Six mortar rounds hammered a centre in the refinery town of Baiji and in Samarra four rockets hit a polling station, police said. South of that city, fighters also launched rocket and mortar attacks on voting offices in Ishaki and Yathrib.
Six mortar shells also shook a voting centre near al-Dujail, police said.
The attacks across Salah al-Din province, a main area of the violence, caused severe damage to the stations, most of them located in schools, police said.
The coordinated strikes were claimed in pamphlets distributed in Tikrit and Samarra by self-declared al-Qaida ally Abu Musab al-Zarqawi's organisation, al-Qaida in the Land of the Two Rivers.
"With the help of God, we have attacked the dens of the apostates who are the pride of the new democracy," the text read.
"These attacks are a warning to all people: They will be targeted."
Meanwhile, Polish troops in central Iraq reported a polling station in Diwaniya had been sprayed with gunfire on Monday night. There were no casualties in the attack.