Iraqis have voted in the first national election since declaring victory over Islamic State (IS).

Key points: Prime Minister Haider al-Abadi, Nouri al-Maliki and an an alliance with paramilitary ties are main contenders

Prime Minister Haider al-Abadi, Nouri al-Maliki and an an alliance with paramilitary ties are main contenders Journalist who threw shoe at George Bush among nearly 7,000 candidates

Journalist who threw shoe at George Bush among nearly 7,000 candidates Results should be known within 48 hours

After weeks of official campaigning, no clear front-runner has emerged, with Prime Minister Haider al-Abadi facing stiff competition from political parties with closer ties to Iran.

Iraq has struggled to find a formula for stability since a US-led invasion toppled dictator Saddam Hussein in 2003, and many Iraqis have lost faith in their politicians.

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

Mr 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.

Haider al-Abadi faces a tough battle to hold on to his leadership. ( Reuters: Mahmoud Raouf Mahmoud )

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

Since then, Baghdad has experienced a relative lull in insurgent-style attacks, but in the lead-up to Saturday's vote Iraqi security forces imposed tight security measures, including a curfew.

Tough competition for al-Abadi

Despite Mr 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.

Whoever the new parliament chooses as prime minister will face an array of challenges after a three-year war against IS which cost the country about $US100 billion ($132.5 billion).

Much of the northern city of Mosul was reduced to rubble in fighting to oust Islamic State, and it will require billions of dollars to rebuild in a stagnant economy.

Sorry, this video has expired Drone footage reveals a devastated Mosul

Mr al-Abadi'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.

The alliance, called "Fatah" — Arabic for "Conquest" — is headed by Hadi al-Amiri, a former minister of transport who became a senior commander of paramilitary fighters in the fight against the IS group.

Many of the candidates on his list were also paramilitary commanders before they cut their official ties with the force in order to seek office.

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

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

Another key player in the vote is influential cleric Muqtada al-Sadr.

He commanded fighters in the war against IS and headed a powerful militia that fought US forces in Iraq before that, but his election campaign has focused on social issues and eliminating government corruption.

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

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

Mr 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.

7,000 candidates for 329 seats

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

Among them is the Iraqi journalist who threw his shoes at US President George W Bush during a news conference a decade ago.

He is now part of a growing push for secular leadership.

Mr al-Zaidi shouted "this is a goodbye kiss from the Iraqi people, dog," as he threw his first shoe at the President. ( Reuters TV )

The vote will be conducted electronically for the first time in an effort to reduce fraud, and polling centres have been set up for many of the country's 2 million people who remain displaced by the war against IS.

Despite the logistical hurdles, the results of the election are expected within 48 hours of the vote, according to the independent body overseeing the election.

Government formation negotiations are expected to drag on for months after that as the dozens of political parties attempt to cobble together a political bloc large enough to hold a majority of seats in parliament.

Reuters/AP