Iraqi army and police personnel have begun voting for a new parliament, two days before the rest of the nation's 22 million registered voters head to polls in the first nationwide elections since the 2011 withdrawal of US forces.

The early voting on Monday is meant to free up the one million-strong military and security forces for election day on Wednesday, so they can protect polling stations and voters.

But as voting got under way, an explosion in El Mansour in Western Baghdad killed five people and injured nine in the latest bout of deadly violence. Police say the blast happened after a device was thrown into a polling station.

The attack appeared to target security personnel voting today.

More than 9,000 candidates are vying for 328 seats in parliament, which is widely expected to be won by an alliance led by Shia Prime Minister Nouri al-Maliki, the Associated Press news agency reported.

Security was tight amid concerns that Sunni fighters, blamed for a recent resurgence of sectarian violence, could target polling stations.

At one central Baghdad polling station, policemen went through four ID checks and search stations before they could enter the building on Monday. Inside, police dogs were used to search for explosives. Some policemen came to cast votes dressed in civilian clothes, to attract less attention, reported AP.

"These are crucial elections that we hope will make things better in Iraq," said one voter, policeman Hatef Yidam. "We want peace and a life with dignity."

Surge in violence

Hospital patients, medical staff and detainees were also voting on Monday. Abroad, Iraqi expatriates in more than 20 countries will also be able to cast ballots for a second day.

Iraq is experiencing a surge in sectarian violence, with Sunni fighters increasingly targeting security forces, army troops and members of the nation's Shia majority.

The resurgence of violence, which nearly tore Iraq apart in 2006 and 2007, underscores the precarious politics of a democratic, but splintered nation.

It also mirrors the three-year-old conflict in neighbouring Syria, where the civil war pits forces loyal to President Bashar Assad whose powerbase stems from followers of a Shia offshoot sect, against mostly Sunni Arab rebels whose ranks are dominated by fighters from al-Qaeda-inspired or linked groups.

The biggest election-related violence in Iraq came on Friday, when a series of bombings targeted an election rally for a Shia group, killing at least 33 people.

The rally for the Iranian-backed Asaib Ahl al-Haq was held at a sports stadium in eastern Baghdad to present the group's parliamentary candidates.

An al-Qaeda breakaway group, the Islamic State in Iraq and the Levant, claimed responsibility for the attack, which triggered a wave of revenge killings late on Friday and Saturday.

On Sunday, 10 people were killed in Baghdad's Shia Sadr City district when a bomb went off at an outdoor market.

Source: AP