Raids on a protest camp in Kirkuk overshadowed early commendations for provincial council elections last weekend, the first since U.S. combat forces left the country in 2011.
At least 100 people have died in violence since Tuesday's attacks, al-Arabiya reports. Nujaifi was quoted as saying the "catastrophe" in Kirkuk was a "flagrant violation of the constitution."
Security forces said they were responding to attacks on nearby military checkpoints while protesters say the military opened fire indiscriminately.
Iraqi Prime Minister Nouri al-Maliki ordered an investigation into the incident, al-Arabiya reports. His Sunni opponents in Anbar province issued a call to arms in response to the incident.
Anbar and neighboring Nineveh province were excluded from last weekend's vote because of the lack of security.
Al-Arabiya reports that nine security officers and three gunmen died during revenge attacks Wednesday.
Director of Middle East programs at Human Rights Watch Sarah Leah Whitson said the Maliki administration has shown it's not holding security forces responsible for their actions.
"The Maliki government's repeated failure to bring anyone to justice has fueled the violence and failed the families of those killed," she said in a statement.
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