An Iraqi electoral official was killed in a roadside bombing yesterday, police said, as two Sunni Muslim-dominated provinces went to the polls under tight security.

Most Iraqis voted for provincial councils in April but the Shi'ite Muslim-led government postponed elections in Anbar and Nineveh, citing security concerns after months of protests by the country's Sunni minority.

The decision to delay voting in those governorates was criticised by the United States, which said this would compound a sense of Sunni marginalisation that has fuelled a wave of violent unrest.

More than 1000 people were killed in militant attacks in Iraq in May, making it the deadliest month since the height of sectarian violence in 2006/7.

A roadside bomb targeted a bus carrying five electoral officials in the town of Baiji in Nineveh, killing one, police said.

In the provincial capital Mosul, a mortar round was fired at a checkpoint near a voting centre, wounding two soldiers.