Iraqi soldiers and policemen cast their ballots for provincial elections on Saturday, a week ahead of the main vote that comes amid an uptick in violence and a long-running political crisis.

The credibility of the elections, the first since March 2010 parliamentary polls, has been drawn into question following deadly attacks on candidates and a government decision to partly postpone voting that means only 12 of Iraq's 18 provinces will take part.

At least a dozen election hopefuls have been killed while others have been wounded or kidnapped in the run-up to the polls. Although security has markedly improved since the height of Iraq's confessional conflict, March was still the deadliest month since August, according to AFP figures.

More than 8,000 candidates are standing in the elections, with 378 seats on provincial councils up for grabs. An estimated 16.2 million Iraqis are eligible to vote, among them about 650,000 members of the security forces.

"We have done our duty, and now we hope that they (candidates) will do their duty also," said federal police Colonel Abbas Kadhim, who cast his ballot in west Baghdad.

"We wish that they will fulfil the hopes of the Iraqi people."

Election centres where voting was completed closed at 5:00 pm (1400 GMT), although those where security forces were still waiting to vote could remain open later, an official from Iraq's Independent High Electoral Commission (IHEC) said.

Voters persistently complain about poor basic services such as electricity and sewerage, rampant corruption and high unemployment.

The latest elections come with the country mired in a political crisis that has pitted Prime Minister Nuri al-Maliki against several of his erstwhile national unity cabinet partners, and amid more than three months of anti-government protests by the country's Sunni Arab minority.

The polls are seen as a key barometer of Maliki's popularity ahead of parliamentary elections next year.

The premier has battled allegations from his opponents of monopolising power, and little in the way of landmark legislation has been passed by parliament, but Maliki insists he is attempting to make the most out of an unruly coalition.

Provincial councils are responsible for nominating governors who take charge of the provinces' administration, finances and reconstruction projects.

The police also ostensibly fall under provincial remit, but the federal government has typically held sway over security matters.

Six provinces will not vote in the polls -- the three of the autonomous Kurdistan region, the disputed northern province of Kirkuk, and two Sunni-majority provinces where authorities say security cannot be guaranteed.