Tens of thousands of Iraqis surged into the streets in at least a dozen demonstrations across the country, storming provincial buildings, forcing local officials to resign and freeing prisoners, the Washington Post reported.
The protesters, including Sunnis, Shias, Kurds and Christians, were demanding adequate electricity, clean water, healthcare facility and jobs in the war-ravaged country.
The protests - billed as Iraq's "Day of Rage" - represented a new sort of conflict for a population that has been menaced by sectarian militias and suicide bombers.
According to officials and eyewitnesses, six people were killed in Fallujah and six in Mosul. Other deaths were reported in five separate incidents across the country.
At least three people were killed in Baghdad, while two were reported dead in Kurdish region of Iraq's north, the Post said citing witnesses.
The protesters, who are believed to have been inspired by the recent revolts in Tunisia and Egypt, forced the resignation of the governor of the southern province of Basra and the entire city council of Fallujah.
The demonstrators seized a police station in Kirkuk, set fire to a provincial office in Mosul and rattled fences around the local governate offices in Tikrit, prompting security forces to open fire.
Iraq has been witnessing a US-led military campaign which began in 2003, leading to the end of president Saddam Hussein's regime in 2006. The US-backed interim-government led by Prime Minister Nouri al-Maliki held its first election last year.
The US President Barack Obama has announced that he will withdraw American troops from Iraq by the end of this year, handing over the task of reconstructions to the Iraqi government.