More than 33 others were also wounded in apparently coordinated bombings targeting Shia places of worship or Husseiniyahs in Kirkuk on Friday, AFP reported.
Two children are reported to be among the dead.
Iraqi security officials say at least three Husseiniyahs, including Khezal al-Tamimi Husseiniyah which is the site of powerful Shia cleric Muqtada al-Sadr's main office in Kirkuk, were attacked.
Bomb attacks and shootings have increased in Iraq over the past weeks.
On Wednesday, at least three people were killed and four others injured in separate attacks targeting Iraqi officials and security forces.
However, July remains the bloodiest month in Iraq in almost two years. Official figures put the number of people killed in attacks in July at 325, the highest monthly death toll since August 2010.