Six protesters were shot dead on Thursday in the southern Iraqi city of Nasiriyah, a health official said, the deadliest incident yet in three days of nationwide demonstrations.
Another 56 people were wounded in the protest, regional health chief Abdulhussein al-Jaberi told AFP.
A total of 27 people, including two police officers, have been killed since demonstrations against unemployment and corruption erupted in Iraq on Tuesday.
Last night, 11 people, including a policeman, were killed during protests in two southern Iraqi cities, police and medical sources said Thursday.
Seven protesters and a policeman died in Nassiriya during clashes between demonstrators and security forces. Four more people were killed in the city of Amara, the sources said.
Iraqi security forces fired live rounds early Thursday to break up protests help for the third day in Baghdad, an AFP photographer said, despite a curfew in effect since dawn.
A few dozen protesters were burning tires in the capital's central Tahrir Square but riot police encircled them, pushed them into side streets and fired in the air, the photographer said.
The unrest spread quickly from small-scale protests in Baghdad on Tuesday over jobs, services and government corruption. At least two people were killed that day as security forces opened live fire and shot water cannon and tear gas. Five more were killed on Wednesday, including a child. Hundreds have been wounded including demonstrators and police.
Abdul Mahdi ordered a curfew in Baghdad from 5 a.m. (0200 GMT) on Thursday until further notice.
The protests are the biggest against Abdul Mahdi's government which took office nearly a year ago, and the biggest in the country since September 2018.
Travelers to and from Baghdad airport, ambulances, government employees in hospitals, electricity, and water departments, and religious pilgrims are exempt from the curfew, the statement said. It was up to provincial governors to decide whether to declare curfews elsewhere.