Demonstrators criticised lawmakers' retirement benefits, which amount to thousands of dollars a month each and stand in marked contrast to the daily struggle for many Iraqis who lack dependable electricity and sewerage services.
But heavy security measures in Baghdad and the southern city of Nasiriyah drew protesters' ire as well.
Hundreds of demonstrators turned out in the capital, as well as several southern cities including Basra, Hilla, Najaf and Nasiriyah, as well as Kirkuk and Baquba, to the north of Baghdad, with Prime Minister Nuri al-Maliki later throwing his weight behind the rallies.
"A huge amount of money goes to these people," said Aamer Qasim, a pharmacist who attended a demonstration in the centre of Baghdad with several colleagues.
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"The money should be spent on health, on education, on electricity, on infrastructure."
Abbas Kadhim, a teacher protesting in Basra, said: "It is not reasonable for a person to work for four years, and then to take 80 per cent of his salary. That does not happen anywhere in the world."
Iraqi lawmakers have faced consistent criticism for their lavish pay and benefits, which are several times that of the average citizen, as well as a failure to pass any significant legislation in years.
But anger has grown in recent weeks in particular over the pensions awarded to them after they leave parliament.
MPs are allotted a base salary of around USD 10,000 per month, and a monthly budget of more than USD 20,000 for security, rent and stationary. They retain around 80 per cent of their full salary as a pension after serving one term in parliament, along with allotments for security, and also get to keep diplomatic passports.