Tens of thousands of Iraqis thronged central Baghdad on Friday, demanding the root-and-branch downfall of the political elite in the biggest day of mass anti-government demonstrations since the fall of Saddam Hussein.

One woman died after she was struck in the head by a tear gas canister, Iraq's human rights commission said, and at least 155 people were wounded on Friday as security forces used tear gas and rubber bullets on protesters camped out in the capital's Tahrir Square.

Five people died on Thursday night from similar injuries.

Protests — in which 250 people have been killed over the past month — have accelerated dramatically in recent days, drawing huge crowds from across Iraq's sectarian and ethnic divides to reject the political parties that have been in power since 2003.

Thousands have been camped out in the square, with many thousands more joining them by day. Friday, the Muslim main day of prayer, drew the biggest crowds yet, with many taking to the streets after worship.

Demonstrators are condemning elites they see as deeply corrupt, beholden to foreign powers and responsible for daily privations.

The protests have been comparatively peaceful by day, becoming more violent after dark.

Clashes have focused on the ramparts to the Republic Bridge, leading across the Tigris River to the heavily fortified Green Zone of government buildings, where the protesters say out-of-touch leaders are holed up in a walled-off bastion of privilege.

An Iraqi demonstrator caries bottles of soda used to neutralize tear gas during protests in Baghdad on Friday. Five people died overnight as a result of injuries sustained in clashes, officials say. (Thaier Al-Sudani/Reuters)

"Every time we smell death from your smoke, we yearn more to cross your republic's bridge," someone wrote on a nearby wall.

Amnesty International said Thursday that security forces were using "previously unseen" tear gas canisters modelled on military grenades that are 10 times heavier than standard ones.

"We are peaceful, yet they fire on us. What are we, Islamic State militants? I saw a man die. I took a tear gas canister to the face," said one 21-year-old, named Barah, whose face was wrapped in bandages.

U.S. Secretary of State Mike Pompeo on Friday urged all sides to reject violence, adding that Iraq's official inquiry into the early October violence "lacked sufficient credibility."

"The Iraqi people deserve genuine accountability and justice," Pompeo said in a statement. "The Government of Iraq should listen to the legitimate demands made by the Iraqi people."

'A mini state'

In Baghdad, protesters had set up checkpoints in the streets leading into and surrounding Tahrir Square, redirecting traffic. Young people swept the streets, many sang about the sit-in, and helmets and gas masks were a common sight.

A woman pushed her baby in a stroller draped with an Iraqi flag while representatives from several Iraqi tribes waved banners pledging support for the protesters.

Mohammed Najm, an engineering graduate currently without a job, said the square had become a model for the country he and his comrades hope to build.

"We are cleaning streets; others bring us water, they bring us electricity, they wired it up. A mini state. Health for free, tuk-tuks transporting for free," he said. "The state has been around for 16 years and what it failed to do we did in seven days in Tahrir."

Despite Iraq's oil wealth, many live in poverty with limited access to clean water, electricity, health care or education. The government of Prime Minister Adel Abdul Mahdi, in office for a year, has found no response to the protests.

An Iraqi demonstrator receives medical help after being affected by tear gas during the protests in Baghdad. (Thaier Al-Sudani/Reuters)

Iraq as a proxy?

In his weekly sermon, top Shia cleric Grand Ayatollah Ali al-Sistani warned of "civil conflict, chaos and destruction" if the security forces or paramilitary groups crack down on the protests. He gave an apparent nod to protesters who say the government is being manipulated from abroad, above all by Iran.

"No one person or group or side with an agenda, or any regional or international party, can infringe upon the will of Iraqis or force an opinion upon them," al-Sistani's representative said during a sermon in the holy city of Karbala.

Reuters reported this week that a powerful Iran-backed faction had considered abandoning Abdul Mahdi, but decided to keep him in office after a secret meeting attended by a general from Iran's Revolutionary Guard. An Iranian security official confirmed the general, Qassem Soleimani, had attended Wednesday's meeting, to "give advice."

Many see the political class as subservient to one or another of Baghdad's main allies, the United States and Iran, who use Iraq as a proxy in a struggle for regional influence.

"Iraqis have suffered at the hands of this evil bunch who came atop American tanks, and from Iran," said protester Qassam al-Sikeeni. "Qassem Soleimani's people are now firing on the Iraqi people in cold blood."

Iraqi President Barham Salih said on Thursday that Abdul Mahdi would resign if parliament's main blocs agreed on a replacement.

Protesters say that wouldn't be enough; they want to undo the entire post-Saddam political system which distributes power among sectarian parties.

"So what if [Abdul Mahdi] resigns? What will happen? They will get someone worse," said 26-year-old barber, Amir.

There were also protests in other provinces, with the unrest having spread across much of the southern Shia heartland.

In the southern city of Diwaniya, roughly 3,000 people, including many families with small children, were out.

Earlier, protesters in oil-rich Basra tried to block the road leading to the Majnoon oilfield and pitched a tent but operations were not interrupted, oil sources said.