Iraqis began voting in a key election for a new parliament as the country slides deeper into violence more than two years after U.S. forces left.

Polls across the Arab nation opened at 7 a.m. local time on Wednesday and will close at 6 p.m. The first national ballot after the Americans left in 2011, the election is being held amid tight security provided by hundreds of thousands troops and police.

Iraq's 22 million registered voters are electing a 328-seat parliament.

A Shiite party led by Nouri al-Maliki, Iraq's prime minister of eight years, is expected to win the most seats but is unlikely to win a majority. Al-Maliki will have to cobble together a coalition if he is to retain his job for a third, four-year term.