Security personnel cast their ballots nationwide Monday ahead of Iraq's first election since US troops withdrew, amid attacks on voting centres and fears the country is slipping into all-out conflict.

Soldiers and policemen queued up at schools across Baghdad and around the country as polling stations opened at 7:00 am (0400 GMT), leaving with the traditional purple ink-stained finger indicating they had cast their vote.

Prime Minister Nuri al-Maliki, lambasted by critics for allegedly consolidating power and targeting minority groups amid a deterioration of security, is bidding for a third term in the April 30 polls with Iraqis frustrated over poor basic services, rampant corruption and high unemployment.

The month-long campaign has seen Baghdad and other cities plastered with posters and decked out in bunting, as candidates have taken to the streets, staged loud rallies and challenged each other in angry debates.

I have come to vote "for the sake of Iraq, and to change the faces who have not served Iraq," said Ahmed, a policeman wearing civilian clothes who was queueing at a polling station in central Baghdad and declined to give his full name.

"We want to choose better people."

Along with more than 800,000 members of the security forces who are eligible to vote at upwards of 500 polling centres nationwide, hospital and prison staff, patients and inmates will also vote on Monday.

The election commission meanwhile said that more than 60,000 ballots had so far been cast in out-of-country voting which continues through Monday.

Attacks on candidates, election workers and political rallies have cast a shadow over the election, however, and parts of the country that have been out of government control for months will not see any ballots cast.

On Sunday alone, five voting centres in the northern city of Kirkuk were attacked by militants, while authorities have announced a week of public holidays to try to bolster security for the election.

The unrest is the latest in a months-long surge in violence that has claimed nearly 3,000 lives already this year, while anti-government fighters have held control of an entire town a short drive from Baghdad since the beginning of the year.

- Long list of grievances -

Although voters have a long list of grievances, from poor electricity and sewerage services to pervasive graft and difficulties securing jobs, along with the near-daily violence, the election has centred around Maliki and his efforts to retain power.

His opponents, who span the communal spectrum, accuse him of shoring up his power base, while minority Sunnis in particular say the 63-year-old Shiite Arab discriminates against them.

Maliki contends that foreign interference is behind deteriorating security and complains that he has been saddled with a unity government of groups that snipe at him in public and block his legislative efforts.

But according to analysts and diplomats, with a fractious and divided opposition and no clear replacement, he remains the frontrunner in the first national election since 2010, and the first since US troops withdrew in December 2011.

Aziz Jabr, a political science professor at Baghdad's Mustansiriyah University, said the stakes were high for Maliki, warning that were he to lose his post, anger over decisions made during his eight years in power could compel his successor to seek retribution in court.

But, Jabr added, "the fissures that have emerged in the Shiite community in the past four years have not helped highlight another Shiite leader against Maliki."

Though not codified, Iraq's leaders have established a de facto agreement whereby the prime minister is a Shiite, the president a Kurd, and the speaker of parliament a Sunni Arab.

No single party is likely to win an absolute majority, however, and as in previous elections, coalition talks are expected to take months as the main positions of power are typically negotiated in one encompassing package.