At least 18 military servicemen were killed in an ambush in western Iraq, including several top-ranking officers, security sources have told Al Jazeera.

The killings took place on Saturday in the Huran valley of the Sunni Muslim-dominated province of Anbar, when a convoy of the army's Seventh Division was hit by the members of the Islamic State of Iraq, the military wing of al-Qaeda, according to sources.

The commander of the army division and his aide were among those killed in the attack.

Posts on online forums dominated by fighters called the slain commander, Mohammed Ahmed al-Kurwi, a "criminal" and celebrated the attack, which security sources described as carefully planned and executed.

The circumstances of Saturday's attack are disputed, with the Defence Ministry saying Kurwi, commander of the Seventh Division, and several other high-ranking officers were killed by a roadside bomb while pursuing fighters from an al-Qaeda training camp in Anbar's desert.

But other military sources said the officers were killed when three suicide bombers wearing explosive belts detonated

themselves among them in the western town of Rutba, 360km west of Baghdad.

"All that we know so far is three suicide bombers wearing explosive vests came from nowhere and detonated themselves among the officers," a military officer who was at the scene told Reuters by phone.

Some security officials suggested informants may have lured the commanders to the area under the pretext of raiding the al-Qaeda camp.

Rising violence

No specific group immediately claimed responsibility for the attack, but suicide bombing is the trademark of al-Qaeda's Iraqi affiliate, which merged this year with counterparts in Syria to form the Islamic State of Iraq and the Levant (ISIL).

The assistant commander of the Seventh Division, the commander of its 27th Brigade, and several other high-ranking officers were also among those killed in the attack, sources said. Another 32 soldiers were wounded.

Violence has been on the rise in Iraq since a deadly security offensive on a Sunni protest camp in a northern town in April.

Two years after US troops withdrew from Iraq, violence is at its highest level since 2006-7, when strife between Sunnis and Shia Muslims killed tens of thousands of people.

At least 352 people have died in attacks across the country so far this month, according to an Associated Press news agency count.