Many of the 25 million eligible voters were expected to boycott the polls amid deep distrust in a political class widely blamed for graft, unemployment and crumbling public services in oil-rich Iraq.

Prime Minister Mustafa al-Kadhemi's future hangs in the balance, with few observers willing to predict who will come out on top after the lengthy backroom haggling between political factions that usually follows Iraqi elections.

"This is an opportunity for change," the premier promised, casting his ballot in Baghdad's fortified Green Zone. "Get out there and vote, change your reality, for Iraq and for your future."

But few shared the enthusiasm, even among those who queued early in the fifth election since the 2003 US-led invasion ousted dictator Saddam Hussein with the promise of bringing freedom and democracy.

"I have come to vote to change the country for the better -- and to change the current leaders, who are incompetent," said housewife Jimand Khalil, 37.

"They made a lot of promises to us but didn't bring us anything."

- 'Corrupt horse-trading' -

The election was held under tight security in a country where the major parliamentary blocs have armed factions and Islamic State group jihadists have launched deadly suicide attacks this year.

Voters were searched twice at polling stations. Travel between provinces was banned and restaurants, shopping centres and airports closed for the day.

The UN and EU sent dozens of election observers.

"Iraqis should have the confidence to vote as they please, in an environment free of pressure, intimidation and threats," said the UN mission in Iraq.

But the vote was marred by technical problems at some stations, including malfunctioning equipment and fingerprint readers, said the prime minister's office and AFP journalists.

One soldier was killed and another wounded by "accidental fire" from a fellow soldier at a polling station in Diyala province, east of Baghdad, according to an official statement.

Polls were set to close at 6:00 pm (1500 GMT), with preliminary results expected within 24 hours but subsequent negotiations likely to take weeks.

A new single-member constituency system for electing Iraq's 329 lawmakers is supposed to boost independents versus the traditional blocs largely centred on religious, ethnic and clan affiliations.

But many analysts believe the change will be limited.

"The election will likely result in another fragmented parliament, followed by opaque, corrupt horse-trading among factions to form the next government," wrote researchers Bilal Wahab and Calvin Wilder in an analysis published by the Washington Institute.

"Few expect this election to amount to more than a game of musical chairs, and the (protest) movement's core demands -- curbing systemic corruption, creating jobs and holding armed groups accountable -- are unlikely to be met."

- 'We want change' -

The election is being held a year early in a rare concession to the unprecedented youth-led protest movement that broke out in October 2019 in Baghdad and swept across much of the country.

Tens of thousands took to the streets to vent their rage at corruption, unemployment and other problems, and hundreds lost their lives in protest-related violence.

Dozens more activists have been killed, kidnapped or intimidated since, with accusations that pro-Iran armed groups, many of which are represented in parliament, have been behind the violence.

The movement largely fizzled amid the bloodshed and as the Covid pandemic hit, and the anger has given way to disillusion among many.

"We want change," said one eligible voter, Mohammed, 23, who asked not to have his full name published.

"I have a degree in Arabic literature but I clean the toilet in a restaurant -- it's humiliating."

Observers expect it will take some time for the new balance of power to emerge as the leading factions compete for the support of a larger number of independents.

Iraq by convention has had a Shiite Muslim prime minister, a Sunni parliament speaker and a Kurdish president.

The bloc of populist cleric Moqtada Sadr, already the largest in the outgoing parliament, is predicted to make gains but not enough to dominate the Shiite camp.

Sadr, who resisted US occupation but has also criticised Iranian influence in Iraq, voted in one of his strongholds, the Shiite holy city of Najaf in the country's south.

Another major force is the Fatah Alliance, the bloc representing many Iran-backed Shiite armed groups, which is expected to roughly retain its share of seats.