An Iraqi demonstrator waves an Iraqi flag during an ongoing anti-government protest, in Baghdad

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 have accelerated dramatically in recent days, drawing huge crowds from across Iraq's sectarian and ethnic divides to reject the political parties in power since 2003.

Friday, the Muslim main day of prayer, drew the biggest crowds yet, with many taking to the streets after worship.

By the afternoon tens of thousands had packed the square, condemning elites they see as deeply corrupt, beholden to foreign powers and responsible for daily privations.

Protests have been comparatively peaceful by day, becoming more violent after dark as police use tear gas and rubber bullets to battle self-proclaimed "revolutionary" youths.

At least 250 people have been killed over the past month.

Clashes have focused on the ramparts to the Republic Bridge leading across the Tigris 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.

"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 on Thursday security forces were using "previously unseen" tear gas canisters modelled on military grenades that are 10 times as heavy as 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 Barah, 21, 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."

"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. Helmets and gas masks were now 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, a jobless engineering graduate, 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.

"EVIL BUNCH"

In his weekly sermon, top Shi'ite 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. And 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," Sistani's representative said during a sermon in the holy city of Kerbala.

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 Guards. 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. Qassem Soleimani's people are now firing on the Iraqi people in cold blood," said protester Qassam al-Sikeeni.

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 Adel Abdul Mahdi resigns? What will happen? They will get someone worse," said barber Amir, 26.

There were protests in other provinces, with the unrest having spread across much of the southern Shi'ite 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 Majnoon oilfield and pitched a tent but operations were not interrupted, oil sources said.