Domestic instability coupled with regional tensions could prove to be the final nail in the coffin of Abdul Mahdi's fragile coalition government, sworn in last year as a compromise between rival factions after an inconclusive election.
The protests, which started on Tuesday over unemployment, corruption, and poor public services, have escalated, with many chanting for the "fall of the regime," a slogan first popularized during the 2011 Arab Spring uprisings.
"We are demanding a change, we want the downfall of the whole government," said one protester in Baghdad who declined to identify himself for fear of reprisal.
Three more people were killed or died from their wounds on Wednesday, taking the toll to at least five after as least two people were killed and 200 wounded on Tuesday.
An Interior Ministry spokesman said one child was killed on Wednesday when a protester threw a bottle filled with gasoline at a vehicle carrying civilian passengers in Zafaraniya district of southeast Baghdad.
A protester was shot dead in the southern city of Nassiriya when police opened fire to disperse demonstrators, local health sources told Reuters. Another protester died of their wounds, police and health sources said.
Police and the army opened fire and launched tear gas canisters to disperse hundreds of protesters all over Baghdad.
Protests also erupted all over southern Iraq - heartland of the Shi'ite Muslim majority who after years of voting along sectarian lines are turning on their political leaders for failing to deliver jobs and basic services.
Protesters set fire near the municipality building in Nassiriya and police used live fire to disperse them. In Kut, protesters tried to break into the municipality building, and hundreds were out on the streets of Hilla and Diwaniya while dozens gathered in the Shi'ite holy city of Najaf.
Thousands gathered in the oil-rich city of Basra in front of the provincial administration building but so far protests there were peaceful. There were peaceful protests in Samawa.
Small protests also took place in the northern cities of Kirkuk and Tikrit, as well as the eastern province of Diyala.