The attack comes as the US-backed Iraqi military prepares to expand operations in the province.

Other violence

Earlier on Thursday, attackers killed three local council members in drive-by shootings targeting checkpoints in the Sunni neighbourhood of Azamiyah in northern Baghdad.

In the northern city of Kirkuk, the teenage son of a US-sponsored newspaper editor was killed by what police said might have been a sniper attack aimed at a passing US patrol.

And in Zafaraniyah, a predominantly Shia neighbourhood in Baghdad, Abdul-Rahman Dawood, a leading figure in the prime minister's Dawa party, was wounded in a bomb explosion near his house.