FALLUJA - Gunmen killed 22 Iraqi Shi'ite pilgrims in an ambush in the western province of Anbar on Monday, a police official said.

The pilgrims were travelling from the southern Iraqi city of Kerbala to neighbouring Syria when they were shot at a checkpoint set up by the gunmen, said Major General Hadi Razij, head of Anbar police.

"There was a big bus and a mini bus containing 30 people, including 22 men and 8 women," he told Reuters. "They took the men and they left the women. They killed the 22 men."

An Interior Ministry source put the death toll at 20 men.

While violence has dropped in Iraq from the height of sectarian fighting in 2006-7, killings and bombings remain a daily occurrence more than eight years after the 2003 U.S.-led invasion.

The sprawling desert province of Anbar was the heartland of a Sunni Islamist insurgency after the invasion and its main cities, Ramadi and Falluja, witnessed some of the fiercest fighting of the war.