Masked gunmen stopped the bus full of Shi’ite Muslim police officers and families at what looked like an Iraqi army checkpoint on a western desert highway in the Sunni-dominated province of Anbar.

Two of the gunmen asked passengers one by one where they were from and then shot 14 dead in their seats, leaving one woman alive with a simple message: “Go back and tell them how we are killing you.”

Last week’s bus attack, whose details were recounted by local officials, strengthened fears that Iraq is edging back into sectarian mayhem, with al-Qaeda again striking at will in a drive to provoke civil war.

Baghdad has now banned off-duty officials, police and soldiers from using the desert highway without an escort.

More than 70 people were killed on Monday alone when car bombs and attacks hit cities across northern Iraq. One assault on a police base involving suicide bombers, rockets and gunmen killed 40 people, mostly police and soldiers.

Invigorated by Syria’s Sunni-led revolt and fed by Sunni frustrations at home, al-Qaeda’s Iraqi wing and other insurgents pose a violent challenge to Baghdad’s Shi’ite-led government.

Iraqi officials say that in the desert near Syria men with black jihadi flags are reclaiming their former strongholds to use as staging posts in their deadly campaign.

Suicide bombers wearing explosive belts – a signature of al-Qaeda – are hitting with a frequency not seen in years, implying there is no shortage of recruits ready to sacrifice themselves.

Nearly 2,000 people have died in attacks since April, according to UN figures, in the worst spike of bloodshed since Shi’ite-Sunni bloodletting eased five years ago.