At least 240 people have died and 8,000 left wounded since demonstrations broke out on October 1 over unemployment and corruption, before evolving into calls for government change.

Overnight, at least one protester was killed in the Shiite Muslim holy city of Karbala, according to the Iraqi Human Rights Commission.

The city's forensics chief told AFP a 24-year-old had been shot in the head, but the governor and security forces said it was "categorically false" anyone had died during the rallies.

The chaotic protest movement is unprecedented in Iraq, both because of its apparently independent nature and the ensuing violence, with even the government acknowledging "excessive force" has been used to quell demonstrations.

But they have escalated, and trade unions representing teachers, lawyers and dentists have all declared strikes lasting several days.

In Iraq's southern cities of Hilla, Diwaniyah, Kut and Nasiriyah, most government offices remained closed on Tuesday for lack of staff.

Students gathered in those cities for their third day of demonstrations, ignoring orders by the higher education minister to return to class.

- 'Stay home? No way!' -

And in the capital, protesters were celebrating their resistance to an overnight curfew declared by the military.

They had spent the night in tents or abandoned buildings after thousands flooded the iconic Tahrir (Liberation) Square in cars and on foot as the six-hour curfew went into effect at midnight.

"As we say in Iraq: we want what we can't have," one young protester in a medical mask told AFP.

"When they said they'd come clear Tahrir, everyone came."

Riot police were still blocking a bridge leading from Tahrir to the Green Zone, which hosts government offices and foreign embassies, using tear gas to keep protesters back.

"Their curfew changed nothing," 30-year-old protester Duaa said on Tuesday morning.

"Did the government think we would stay at home? No way," she told AFP.

Like the curfews, reform proposals by Prime Minister Adel Abdel Mahdi have done little to stamp out the rallies, which are now demanding a total government overhaul.

"We don't want this government anymore. We want a transitional government and constitutional change," another female protester said.

"I'm a teacher, I have a salary, I have a house -- but the young unemployed people are my brothers and relatives, too."

- Parliament to meet -

Anger at inequality and accusations that government corruption was fuelling it sparked a six-day burst of protests in Baghdad and the south from October 1.

The rallies turned deadly, with 157 people killed -- most of them protesters in Baghdad -- and thousands wounded, according to a government probe.

A second wave of protests began last week and has since left 83 dead, but swelling numbers of young people have joined anyway.

About 60 percent of Iraq's 40-million-strong population is under the age of 25.

But youth unemployment stands at 25 percent and one in five people live below the poverty line, despite the vast oil wealth of OPEC's second-largest crude producer.

Parliament is set to meet again on Tuesday to discuss reforms, a day after it voted to dissolve Iraq's provincial councils and summon Abdel Mahdi for questioning.

They were the first major decisions in weeks by the 329-member legislative body, which has been paralysed by the protests.

In solidarity with demonstrators, four lawmakers resigned late on Sunday, and the largest parliamentary bloc launched an open-ended sit-in over the weekend.

Saeroon, the bloc tied to firebrand cleric Moqtada Sadr, said it was dropping its support for Abdel Mahdi.

The move has left the premier more squeezed than ever, as Saeroon was one of the two main sponsors of his government.

The other was Fatah, the political arm of the Hashed al-Shaabi paramilitary force, which has said it would continue to back the central government.

Several Hashed offices have been torched in recent days in southern Iraq, prompting vows of "revenge" from its leaders.