The bomber rammed his explosives-packed vehicle into a police station in the town of Dibis northwest of the northern oil city of Kirkuk, district official Abdullah al-Salehi told AFP.
Sadiq Omar Rasul, the head of the Kirkuk health department, said the bombing killed three people and wounded 165. Many of the injured were pupils at an adjacent Kurdish girls' secondary school, according to Salehi.
Dibis is part of a swathe of territory that the Kurds want to join to their autonomous region in northern Iraq, over the objections of the federal government in Baghdad.
Diplomats say the dispute poses the biggest threat to Iraq's long-term stability.
Nine other people were killed in separate attacks on Monday in Iraq, including the driver of the minister of the environment, Serkun Slewah, an employee of the health ministry and an employee of the trade ministry.
Gunmen also killed a blacksmith near Baquba, north of Baghdad, and shot dead Bahjat Mustafa, a candidate for the provincial councils elections, in the main northern city of Mosul, where two policemen were also killed.
The violence came a day after attacks killed 11 people, including an anti-government protest organiser and a city council member.
Violence has decreased from its peak in 2006 and 2007 when sectarian bloodshed raged between Sunni and Shiite Arabs.
But 10 years after the US-led invasion, attacks remain common, killing 220 people last month, according to an AFP tally based on security and medical sources.