Eleven protesters died on October 25 while setting fire to the headquarters of a powerful armed faction in the southern Iraqi city of Diwaniyah, a security source told AFP.
The fire at the Badr organisation's offices was the deadliest incident yet on October 25, when anti-government rallies resumed across the country.
The Iraqi Human Rights Commission said another 30 demonstrators died and more than 2,000 were wounded by gunfire and tear gas in protests in Baghdad and the country's south.
The demonstrations represent a second phase of a week-long movement in early October demanding an end to corruption, unemployment and an overhaul of the political system.
Activists urged Iraqis to return to the streets on October 25, which marks a year since Prime Minister Adel Abdel Mahdi came to power.
“We’re not hungry —we want dignity!” a protester shouted in Baghdad.
