A total of 329 seats are up for grabs in the election, which was moved forward from 2022 as a concession to youth-led pro-democracy protests that erupted in late 2019.

But many voters are expected to stay away amid widespread anger over corruption and ineffectual governance that has failed to meet the aspirations of Iraq's 40 million people, 60 percent of whom are aged under 25.

There are fears voter turnout could drop below the 44.5 percent figure registered in 2018.

More than 25 million citizens are eligible to vote. They are supposed to present a biometric card for what was conceived as a fully electronic voting process.

However, some voters have not received the cards and authorities say provisions have been made to ensure they are not excluded.

More than 3,240 candidates are in the running, including 950 women.

One quarter of seats are reserved for female candidates, and nine for minorities including Christians and Yazidis.

A new single-member constituency system is supposed to boost independents and reduce traditional political blocs, largely centred on religious, ethnic and clan affiliations.

Two days before polling day, voting will be organised for security forces, displaced citizens and prisoners. This year nationals living abroad will not be voting.

- The major factions -

Groups from Iraq's Shiite Muslim majority have dominated since the overthrow of Saddam's Sunni Arab-dominated government, but they are divided among themselves. There are also groups representing the Sunni Arab and Kurdish minorities.

Here is a look at the main ones.

- Sadrists -

The biggest bloc, with 54 seats in the last assembly, has been led by populist firebrand Shiite cleric Moqtada Sadr, a former leader of anti-US militia.

He has emerged as a vocal critic of crooked and corrupt politicians and inept public authorities, even if his supporters are also active at all levels of the state apparatus.

The Sadr-led Saeroon bloc could strengthen its hold in parliament after scoring big in the 2018 elections.

- Pro-Iran factions -

Candidates representing pro-Tehran paramilitary groups were elected to parliament for the first time in 2018, a year after their fighters were key in defeating Islamic State jihadists.

The Conquest Alliance is led by Hadi al-Ameri, who also heads the Badr organisation, one of the factions of the Hashed al-Shaabi, former paramilitaries now integrated into the regular forces.

Another major player is Houqouq, which is close to the Hezbollah Brigades, another group under the Hashed umbrella.

Former prime minister Nuri al-Maliki, who led Iraq from 2006 to 2014, heads the State of Law Alliance.

The Alliance of State Forces brings together the groups of former prime minister Haider al-Abadi, who led the fight against the IS, and Ammar al-Hakim, who leads the moderates in the Shiite camp.

- Sunni groupings -

The influential speaker of parliament, Mohammed al-Halbusi, leads the successful Taqaddum (Progress) movement that draws support from the mainly Sunni Arab west of Iraq.

Their main competitor is the Azm (Determination) movement of controversial Sunni politician Khamis al-Khanjar, who has been sanctioned by Washington and is accused of corruption.

- Kurdish factions -

The two main historic parties are the Kurdistan Democratic Party (KDP) of the Barzani clan and the Patriotic Union of Kurdistan (PUK) of the Talabani clan.

The Kurdish opposition is represented by Jamaa Islamiya, the recently formed "New Generation" movement and Goran (Change).