The security situation in across Anbar province - once a stronghold of Sunni-led attacks on foreign troops and government targets - has improved dramatically since tribal fighters decided in 2006 to turn against al-Qaeda and other groups.

The attack comes less than a month after US troops withdrew from urban centres in line with a security pact between Baghdad and Washington that calls for US forces to leave Iraq by the end of 2011.

Violence had dropped markedly throughout Iraq, but attacks increased in the run-up to the pullback, with 437 Iraqis killed in June - the highest death toll in 11 months.

On Tuesday, Iraqi officials declared a rare vehicle ban across Anbar after two bomb attacks killed three people in the Ramadi, the provincial capital. The previous day, an explosion had killed two police officers in the city.

Elsewhere on Saturday, a bomb planted on a car in the Adhamiya neighbourhood in northern Baghdad, the capital, killed one person and wounded another, police said.