Islamic State (Isis) in Iraq has killed at least 12 members of pro-government forces on the outskirts of Haditha in Anbar province, west of Baghdad.

Military and medical officials told the Associated Press the series of suicide attacks were carried out after IS bombarded army and militia positions with shells. Initially two suicide bombers blew themselves up in close proximity to government forces. Three suicide car bomb attacks followed closely afterwards.

Twelve soldiers and allied Sunni militiamen were killed in the onslaught. Five soldiers and three Sunni tribesmen were also wounded in the attacks.

US-led air strikes destroyed six IS vehicles and killed 13 of the extremist group's fighters in clashes following the initial bombing.

Haditha, a key strategic point on the Euphrates river and the location of a major dam, is one if the last remaining towns under government control in the embattled Anbar province. Ramadi and Fallujah have both fallen into IS hands. The extremist group has tried, without success, to take Haditha in a number of bloody assaults.

The UN has said a total of 1,325 Iraqis were killed and a further 1,811 injured in fighting during August. Of these, 585 were civilians. The number of civilian casualties were lower than those recorded in the previous month, when 844 were killed.

With the exception of Anbar province, where clashes have raged between IS and government forces for two years, the worst of the violence in the country remains reserved for Baghdad province where 318 were killed and 751 have been injured in recent months.

488 members of Iraq's security forces, including Kurdish fighters, the interior ministry's SWAT forces and tribal militiamen, were killed and another 492 were injured in August.