Official results determining the makeup of the 329-seat parliament were expected in the coming days -- while the horse-trading to form a new government looks set to take far longer.

But what has emerged already is that many across the war-scarred nation are fed up with the establishment that has dominated since the 2003 US-led ouster of Saddam Hussein.

"The policies of the last 15 years no longer convince voters," Amir al-Saadi, a politics professor at the University of Baghdad, told AFP.

Official turnout on Saturday was 44.5 percent -- the lowest in any national poll since the US-led invasion -- with Prime Minister Haider al-Abadi angling for a new term after overseeing the fight against IS.

Abadi -- a consensus figure who has balanced off the United States and Iran -- faces several major challengers from within his dominant Shiite community four years after coming to power.

Chief among them is Hadi al-Ameri, a former commander of Iran-backed units that fought IS, who is looking to turn battlefield wins into political gains with his list of ex-combattants.

An official told AFP under condition of anonymity that initial tallies had Abadi's list just ahead of that of Ameri, with an anti-establishment alliance of Shiite cleric Moqtada Sadr and communists in third.

- US-Iran tensions -

The vote came with tensions surging between the US and Iran after Washington's withdrawal from the 2015 nuclear deal, sparking fears of a destabilising power struggle over Iraq.

US Secretary of State Mike Pompeo, whose country still has troops in Iraq from the fight with IS, lauded the poll and called for an "inclusive government, responsive to the needs of all Iraqis".

But swathes of the population -- especially the youth -- appeared to have long given up on that dream.

"Iraqis had the sense that the game was already decided, that the elections were pre-packaged," said Karim Bitar, from the French Institute for International and Strategic Affairs.

On the streets of Baghdad there was little optimism after the vote.

"If the situation remains as it is, nothing will change," truck driver Jameel al-Kabi, who did not vote, told AFP.

"We will get nothing. Look in front of your eyes, there's rubbish in the streets, there's traffic, there's no work."

Others, however, said that a refusal to participate was not the way to fix the situation, even if people were angry.

"There is a corrupt state, a corrupt government, a government of vested interests, why don't I try to do the simplest of things I can to change it?" asked university graduate Mahmoud Sakban, who did cast his ballot.

Turnout was low despite a sharp decrease in violence across the country, with threats from IS against the polls failing to materialise.

Voting was stronger in some areas freed from the jihadist yoke, with people queueing up to cast their ballot in the battered former IS bastion of Mosul.

The US-led coalition that helped battle IS pledged to work with the elected government to ensure the jihadists' "lasting defeat" and said Saturday's poll proved Iraqis "emphatically rejected violent extremism".

- Challenges ahead -

Iraqis were faced with a fragmented political landscape, some five months after the IS was ousted from the country.

Results in the Sunni heartlands once dominated by the jihadists were set to change radically with Shiite-led groupings pushing to make inroads.

Participation was also higher than elsewhere in Kurdish regions, where the traditional political forces have been left in disarray by a disastrous push for independence last year.

Baghdad seized back disputed oil-rich regions in the wake of a controversial referendum, threatening the role of kingmakers typically played by the Kurds on the national stage.

Overall, just under 7,000 candidates stood in the nationwide and Iraq's complex system means no single bloc is likely to get anything near a majority in parliament.

Whoever emerges as premier will face the mammoth task of rebuilding a country left shattered by the battle against IS -- with donors already pledging $30 billion (25 billion euros).

More than two million people remain internally displaced and IS is still able to launch deadly attacks.