BAGHDAD (REUTERS) - Iraqi security forces killed two people on Wednesday (Oct 30) by shooting tear gas canisters directly into their heads in an attempt to stop protesters entering Baghdad's heavily fortified Green Zone, security and medical sources said.

At least 175 people were wounded as protesters from across Iraq's sectarian and ethnic divides thronged the centre of the capital in a show of fury at a political elite they see as deeply corrupt and responsible for widespread economic hardship.

Initially festive street rallies took a violent turn by nightfall when a group of protesters tried to storm a bridge leading to the Green Zone.

A rocket was seen flying towards the Green Zone and a blast was heard coming from that direction. The area houses government buildings and foreign missions. The military said the rocket had crashed inside, killing a member of the security forces.

Iraq's most powerful politicians appeared to withhold support for Prime Minister Adel Abdul Mahdi as anti-government protests have swelled into the biggest mass demonstrations the country has seen since the 2003 fall of Saddam Hussein.

While Abdul Mahdi's fate was not yet clear, demonstrators said removing him would not be enough after four weeks of unrest in which more than 250 people have been killed.

Middle-class families with small children joined self-proclaimed "revolutionary" youths from poor neighbourhoods on Wednesday to brave tear gas and barricades in Baghdad's Tahrir Square.

"No Moqtada, no Hadi!" protesters chanted, denouncing what they perceived as an effort by the leaders of parliament's two largest blocs - populist cleric Moqtada al-Sadr and militia leader Hadi al-Amiri - to cling to power behind the scenes with or without the prime minister they installed a year ago.

Sadr has demanded Abdul Mahdi call an early election. When the premier refused, Sadr called on Amiri, his main political rival, to help oust him.

Amiri issued a statement overnight that was initially seen as accepting Sadr's call to ditch Abdul Mahdi. But a day of silence followed, leaving the premier's fate in the balance.

"We will work together to secure the interests of the Iraqi people and save the nation in accordance with the public good,"Amiri had said in an overnight statement.

Many young women and older people joined the protests as they gained momentum and appeared safer. The mood on Wednesday afternoon was jubilant yet defiant with many singing and dancing and a group of young men even playing dominos.

That contrasted with the tense situation earlier this week when scores were killed nationwide in clashes with security forces.

"We are staying and holding our ground. Our demand is not only to replace Adel Abdul Mahdi, we want the whole government uprooted," said Karar Saad, 20.

"All of them are thieves."

'FALL OF THE REGIME'

Despite promising reforms to help rein in corruption and ordering a broad reshuffle of the cabinet, Abdul Mahdi has done little to address the demonstrators' complaints. Parliament passed measures on Monday including reduced salaries for officials, but protesters derided this as too little too late.

The security forces responded to the initial unrest in early October with a brutal crackdown, firing with live ammunition from rooftops into crowds. But if they hoped to intimidate the demonstrators, the tactic has backfired, inflaming passions.

Despite Opec member Iraq's vast oil wealth, many Iraqis live in poverty or have limited access to clean water, electricity, basic health care and education. Most of the protesters are young people who above all want jobs.

Many Iraqis also see the political class as subservient to one or another of Baghdad's main allies, the United States and Iran. These powers, they say, use Iraq as a proxy to pursue their struggle for regional influence, without concern for the needs of ordinary Iraqis.

While the demonstrations were initially mostly made up of young men, they have become more diverse as the crowds have increased, with more families, women and older people braving streets strewn with tear gas canisters and debris.

"We are a people who love life, we are a country of riches that you steal. We are staying here, women and men, we will not retreat!" said Safaa, a female student. "Leave! Enough! You haven't had enough stealing?"

She called for dismantling the entire system of power sharing among sectarian political parties, put in place after the 2003 US-led invasion that toppled Saddam.

SINGING AND DANCING

The entrance to Tahrir Square was littered with makeshift tents on Wednesday with many protesters camping out there overnight. Young men formed human chains to keep roads clear for a flurry of tuk-tuks, which have been used to ferry the wounded through crowds from the battle lines of clashes with police.

Security forces continued to lob tear gas at protesters on a nearby bridge who sought to break into the Green Zone.

By nightfall, however, the protesters changed tack and attempted to cross a different bridge and were met with more force by the authorities.

Protests took place in five other provinces, mostly in the southern Shi'ite Muslim heartland. Around 800 people gathered in the Shi'ite holy city of Najaf, 500 in Diwaniya and over 1,500 in Nassiriya, where at least 51 people were wounded overnight when security forces opened fire to disperse protests.

Over 2,000 people gathered in oil-rich Basra in the far south, where operations came to a complete standstill at the Umm Qasr commodities port after protesters blocked its entrance the previous day, port officials said.

In the eastern province of Diyala, which borders Iran, 800 protesters gathered in its capital Baquba, setting fire to photos of the late Ayatollah Ruhollah Khomeini, who led Iran's 1979 Islamic Revolution.