It is impossible to predict who will lead Iraq's next government after an election that stands out in the Middle East for its competitiveness.
There are about 6,200 candidates from 86 political groups vying for 325 parliamentary seats.
Sectarian v secular
Nuri al-Maliki, the prime minister, whose State of Law coalition is claiming credit for improved security since the peak of sectarian warfare in 2006-07, faces a challenge from one-time partners looking to recapture Shia support.
He also takes on a secular list tapping into exasperation with years of conflict, poor public services and corruption, and hoping to gain support from a once-dominant Sunni minority.
Iyad Allawi, a former prime minister and a secular Shia who heads the cross-sectarian, secularist Iraqiya list, is already complaining about irregularities in early voting, setting the scene for possible challenges to the election's integrity.
Muqtada al-Sadr, the Shia religious leader, asked his followers on Saturday to turn out and vote in the election.
In a televised address from Tehran, the capital of neighbouring Iran, al-Sadr urged Iraqis to turn out in large numbers and give their support to those who he said were "faithful" to the Iraqi people.
Al Jazeera's Anita McNaught reporting from Baghdad, said: "Perhaps this is a sign that all parties are moving towards a more political and peaceful path and if there is one word that is common amongst all the voters, it is a message of national unity and anti-sectarianism."
No bloc is expected to win a majority, and it may take weeks or months to form a government.
The result could be a dangerous vacuum that armed groups might exploit.
This week, 600,000 people, including soldiers and detainees, voted early, as did Iraqi expatriates and refugees abroad.
Some of Maliki's rivals allege intimidation and arrests, adding to tensions created by a ban on 400 candidates accused of links to Saddam's outlawed Baath party, a furore which exposed the lingering divide between Sunnis and Shia.
"We need to see the will of the Iraqi people fully exercised in this coming election. Otherwise, Iraq will be thrown back to severe violence," Allawi said as he concluded his campaign.
The Islamic State of Iraq, an al-Qaeda affiliate that views the Iraqi government led by Shia Muslims as heretical and unfit to rule, has given warning that Iraqis against voting and vowed to attack those who defy them.
|Iraqis are obliged to dip their finger in ink in order to vote in the elections [AFP]
Violence has killed at least 49 people in the last few days.
Troops and police were out in force across Iraq's 18 provinces.
Strict security measures have come into force - beginning with a curfew on Friday evening in Ramadi and other restrictions that will last for three days.
They include a ban on use of civilian vehicles on election day to try to foil car bombers.
Sunday's vote will also play an important role in Washington's policy in the country.
Iraq's political course will be decisive for plans of Barack Obama, the US president, to halve US troop levels over the next five months and withdraw entirely by end-2011.
The short window between the election and Washington's August 31 deadline for ending combat operations has raised doubts about whether Obama might reconsider his plans, but US officials say that would take an "extraordinarily dire" situation.
The 96,000 US troops remaining in Iraq will stay in the background, underscoring the waning American role in Iraq.
The election will be supervised by as many as 120 international monitors, with a number of foreign embassies providing staff to act as monitors too.
Iraqis living abroad started voting in their country's general election two days before the election.
The Iraqi electoral commission is to announce preliminary results on March 10-11, based on votes from about 30 per cent of the polling stations.
The supreme court would then certify the poll results, after hearing appeals, within about a month of the election, the official said.
After the last national election in 2005, it took Iraq's feuding political parties about five months to agree on a prime minister and for a cabinet to be approved.