BAGHDAD (AFP) - Attacks in Sunni-majority areas of Iraq killed nine people on Sunday, exactly a month ahead of parliamentary polls that remain in disarray after the mass resignations of election commissioners last week.

The violence came hours after seven soldiers were shot dead at a checkpoint in a late-night attack by militants in the north, the latest in a surge in bloodshed that has killed more than 2,200 people already this year.

The unrest has been driven principally by anger in the Sunni Arab minority over alleged mistreatment at the hands of the Shiite-led authorities, as well as by the civil war raging in neighbouring Syria.

A suicide bomber detonated a vehicle packed with explosives on a major bridge in Ramadi, a city west of Baghdad where security forces are still grappling to retain full control after militants took over several neighbourhoods two months ago.

The blast killed seven people and wounded 10 more, and also badly damaged the Hauz Bridge, a key crossing used by civilians connecting the north and south of the city.

Ramadi originally had five bridges across the Euphrates River before a militant surge earlier this year.

But two are used exclusively by security forces, and two others - including the Hauz Bridge - have now been damaged to the point they can no longer be used.

Civilians in Ramadi are now able to use only the Albu Faraj bridge in the north of the city.

Ramadi is the capital of Anbar province, a predominantly Sunni desert region in west Iraq that shares a border with Syria.

In early January, anti-government fighters seized control of parts of the city and all of nearby Fallujah, also in Anbar.

But while security forces have managed to take back most of Ramadi, a stalemate persists in Fallujah, which remains in militant control.