Updated 8.10pm

Polls have closed across Iraq in the first national election since the country declared victory over the Islamic State group.

The vote, the fourth since the 2003 US-led toppling of Saddam Hussein, was marked by reports of low turnout and irregularities.

Results are expected within the next 48 hours according to the independent body that oversees Iraq's election, but negotiations to choose a prime minister tasked with forming a government are expected to drag on for months.

Voting began early Saturday in a contest that had no clear front-runner after weeks of official campaigning.

Iraqi Prime Minister Haider al-Abadi's stiffest competition came from political parties with closer ties to Iran.

Baghdad's streets began to fill up with cars before voting concluded after al-Abadi partially lifted a security curfew in an effort to improve turnout.

Nearly all civilian vehicles had been banned from Baghdad's streets on Saturday morning and many voters complained of having to walk more than two miles to reach polling stations.

Iraq's most senior Shiite cleric spoke out on the issue of voter participation on Saturday, encouraging Iraqis to vote "to prevent the arrival of a corrupt parliament".

"The lack of participation will give the opportunity for others to reach parliament and they will be very far from the aspirations of the people," said Sheikh Abdul-Mahdi al-Karbalai, the representative of Grand Ayatollah Ali al-Sistani, on local Iraqi television from Karbala.

Sistani has repeatedly encouraged Iraqis to vote into power a new political class to combat corruption.

For those who did attempt to vote, some in Baghdad complained of voting irregularities at polling stations linked to a new electronic voting system implemented for the first time this year in an effort to reduce fraud.

Thamer Aref, 45, along with his wife and daughter, were turned away from a polling station north of central Baghdad.

Aref had turned in his old voter ID card months ago for the biometric identification card required by the new system.

However, Aref's biometric card was not ready ahead of Saturday and, with neither card, the polling station did not allow him to a cast a ballot.

"I lost my right to vote," he said.

Associated Press journalists documented several similar cases at a number of different polling stations across Baghdad.

Amira Muhammed, the supervisor of a polling station in Azamiyah, Baghdad, said some people could not vote because they did not pick up their new biometric ID cards in time.

"The problem is not with us," she said.

In central Baghdad, voters supporting al-Abadi said they were doing so because they gave him credit for Iraq's military victory over IS.

Al-Abadi "took revenge" for civilians killed in insurgent attacks in Iraq "with the victory over Daesh", said 71-year-old Felihah Hassan, using the Arabic acronym for IS.

After IS overran nearly a third of Iraq in the summer of 2014, the group launched waves of suicide bombings targeting civilians in Baghdad and other pockets of government-controlled territory.

With support from the US-led coalition and Iran, al-Abadi oversaw a gruelling war against the extremists and declared victory over the group in December.

Despite al-Abadi's military achievements, Iraq continues to struggle with an economic downturn sparked in part by a drop in global oil prices, entrenched corruption and years of political gridlock.

The prime minister's most powerful opponents are his predecessor, Nouri al-Maliki, and an alliance of candidates with close ties to the country's powerful, mostly Shiite paramilitary forces.

Jassim Mohsen, 58, who fought against IS with the paramilitary forces, said he was casting his vote for the alliance with paramilitary ties because of their personal sacrifices.

"I elected the Fatah list because they are the only ones who fought Daesh and gave blood," he said.

Some Sunnis voting said they were hopeful this election would help Iraq move beyond sectarian politics and become more inclusive.

Marginalisation of Iraq's Sunnis under al-Maliki is seen as a factor that allowed IS to rise in power in Iraq.

Al-Abadi has led a more cross-sectarian government marked by his ability to balance the interests of his two allies often at odds: the US and Iran.

The war left more than two million Iraqis, mostly Sunnis, displaced from their homes, with cities, towns and villages suffering heavy destruction.

Abdulrazaq Kubi and his wife Suheila Mahdi, both Sunnis from Baghdad, said they would not be voting for al-Abadi, casting their votes instead for a Sunni-led political alliance.

"The victory is not 100%, there is still Daesh here," said Mahdi.

The government "is neglecting the refugees because they are Sunni. They left them in the camps, in the winter it floods, in the summers, they go hungry", she added.

In total there are 329 parliament seats at stake, with nearly 7,000 candidates from dozens of political alliances.

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