For nearly two months, the country's capital and Shiite-majority south have been gripped by the largest protests since the 2003 US-led invasion that toppled Saddam Hussein.

The rallies have paralysed daily life in many towns and cities, with schools intermittently closed, streets shuttered and government offices empty.

On Wednesday, religious authorities in Iraq's holy city of Karbala ordered their network of private schools there, as well as in nearby Babylon and the second holy city of Najaf, kept shut for two days.

They feared a repeat of the previous day's chaos, when anti-government demonstrations devolved into clashes between riot police and protesters, leaving one dead.

Karbala, visited by millions of Shiite pilgrims from around the world each year, had seen deadly skirmishes at night, but they have increasingly spilt over into the day.

By mid-morning on Wednesday, demonstrators were back in the streets, torching tyres inside Karbala and around its edges that sent thick columns of black smoke into the air.

In Nasiriyah, further south, local authorities ordered all public offices closed for two days, although they had been largely shut already by ongoing sit-ins and marches.

- '16 years in chaos' -

Iraq's street violence has left more than 350 people dead and around 15,000 wounded in the last two months.

Another 100 protesters suffered injuries in two days of rallies in Hillah, just south of Baghdad, when security forces began using tear gas against demonstrators.

Activists also cut roads with flaming tyres in the protest hot spots of Kut and Najaf, keeping government employees from reaching work in relatively peaceful sit-ins.

In Diwaniyah and the oil-rich port city of Basra, no security forces could be seen as demonstrators hit the squares and streets.

Picketers outside Basra also sealed off the entrance to the Nasiriyah oil field, a contributor to Iraq's exports of some 3.6 million bpd.

The country is OPEC's second-largest crude producer and the oil exported through Basra's offshore terminals funds more than 90 percent of the government's budget.

The industry has so far remained relatively insulated from the unrest, but Basra's residents are seething over their city's notoriously poor water provision, unstable electricity and sub-par public schools.

"It's been 16 years that we've been living in chaos and corruption," one protester told AFP on Wednesday.

"Basra should have been a wealthy city, but instead its a trash dump."

Corruption is rampant in Iraq, ranked the world's 12th most corrupt country by Transparency International.

A government probe found that $450 billion in public funds had been lost to graft, fake contracts and ghost employees since 2003.

One in five Iraqis live in poverty and youth unemployment is at 25 percent, according to the World Bank.

- 'We don't want them' -

Those rates were among the driving forces behind the latest wave of protests.

"The government has lost all its legitimacy. We don't want them," another Basra demonstrator said.

"They meet every day and claim to be discussing our demands, but we expect nothing from them."

In central Baghdad, young demonstrators donned helmets and medical masks to again face off with security forces unleashing tear gas.

A major flashpoint has been the historic Rasheed Street and its nearby colonnaded alleys, where riot police have clashed with demonstrators.

Police have sought to keep the protesters from reaching the nearby Al-Ahrar bridge that crosses the river Tigris toward key government buildings on the western side.

One protester was killed near the bridge on Tuesday, but hours later, Baghdad was rocked by another kind of violence: three explosions that left six dead.

The near-simultaneous blasts were caused by explosives-laden motorcycles and roadside bombs in Shiite neighbourhoods, according to medical and security sources.

They were the first such blasts in Baghdad in several months, but there was no immediate claim of responsibility.