Iraqis voted on Saturday in the country's first polls since US troops departed, a key test of its stability in the face of a spike in attacks that has claimed more than 100 lives.

But the credibility of the provincial elections has come into question, with attacks on candidates leaving 14 dead and a third of Iraq's provinces -- all of them mainly Sunni Arab or Kurdish -- not even voting.

"I came this early because I was very excited to vote. I think some of the current provincial council members did not do a good job," university student Abdulsahib Ali Abdulsahib, 22, told AFP at a polling station in central Baghdad after voting began at about 7:00 am (0400 GMT).

"Security is the most important problem that all of them should be working for; without this, life would be so difficult. I hope this is the first thing they work towards."

Voters were searched twice before being allowed to enter, and Iraqi security forces had a heavy presence in the area. Only pre-approved vehicles were allowed on the streets, which were largely deserted except for police and soldiers.

The elections are the first since parliamentary polls in March 2010 and also the first since US troops withdrew in December 2011.

An estimated 13.8 million Iraqis are eligible to vote for more than 8,000 candidates, with 378 seats being contested.

Every Iraqi who votes "is saying to the enemies of the political process that we are not going back," Prime Minister Nuri al-Maliki said on state television after casting his ballot at the Rasheed Hotel in Baghdad's heavily fortified Green Zone.

"I say to all those who are afraid for the future of Iraq and afraid of a return of violence and dictatorship that we will fight by casting ballots," Maliki said.

The polls are seen as a gauge of Maliki's popularity ahead of a general election next year, but major issues affecting voters such as poor public services and rampant corruption have largely been ignored during the campaign.

"I don't believe this election will provide a magic solution for the problems of Iraqis, and the problems in the country," said Ihsan al-Shammari, a politics professor at Baghdad University.

But, he said, a well-run vote with a high turnout could bolster Iraqi belief in democracy a decade after US-led forces ousted now-executed dictator Saddam Hussein.

The lead-up to the vote was blighted by a rise in violence that left more than 100 people dead in the past week and 14 election candidates killed since campaigning began.

Six of Iraq's 18 provinces are not participating -- two because authorities say security cannot be ensured, and four because of various political disagreements.

Those two factors have led diplomats to worry about the credibility of the election, as they could result in low voter turnout, leading to results that are unrepresentative or not broadly accepted.

Iraqi forces were responsible for security on polling day, the first time they have been in charge without support from American or other international forces during elections since Saddam was toppled.

"We will use all of our forces in the interior and defence ministries to control the situation," said interior ministry spokesman Brigadier General Saad Maan.

While violence in Iraq has fallen significantly since the height of its sectarian war, it still faces significant security challenges, mainly from Sunni militants linked to Al-Qaeda who launch attacks in a bid to undermine confidence in the Shiite-led government.

Provincial councils are responsible for nominating governors who take charge of the provinces' administration, finances and reconstruction projects, and have sway over key local issues such as sewerage and other services.

But while several contentious issues fall under the purview of the provinces, campaigning is rarely on ideological or policy lines. Candidates generally appeal to voters on the basis of shared sectarian, ethnic or tribal identities.

As a result, many key concerns such as poor public services, widespread corruption and high unemployment have gone largely unaddressed.