An Iraqi police officer, who survived a shooting more than a decade ago, cast her ballot on Thursday in early voting ahead of Iraq's parliamentary elections on May 12.

First Lieutenant Zahra Obeid survived a militant ambush on her team while on patrol in Baghdad in 2007.

Arriving to vote on Thursday she said that the incident had not deterred her from carrying out her duties, but instead strengthened her determination.

Obeid voted at a primary school in the east of Baghdad in a preliminary round of voting arranged for security forces, prisoners, and medical patients.

The independent body that oversees Iraq's elections says thousands of people are expected to cast their ballots before polls close on Thursday evening.

There is no clear front-runner in the upcoming elections, with Iraq's current prime minister Haider al-Abadi facing stiff competition from political alliances with closer ties to Iran.

Nearly 7,000 candidates are vying for 329 parliament seats.

No single alliance appears capable of winning a majority.

Instead months of negotiations are expected to follow Saturday's vote to form a government.

The vote will be the first since Iraq declared victory over the Islamic State group and the fourth since the 2003 US-led toppling of former Iraqi president Saddam Hussein.