BAGHDAD - A series of coordinated bombings targeting Shiite pilgrims ahead of major commemoration rituals were the deadliest in attacks across north and west Iraq that killed 18 people on Wednesday.
The bloodshed is the latest in a months-long surge in violence that authorities have so far failed to stem despite several operations against insurgents, and have forced Prime Minister Nuri al-Maliki to appeal for help from Washington in combating militancy.
Wednesday's violence came on the eve of annual ceremonies marking the anniversary of the death of a key figure in Shiite Islam, a period during which Sunni militants typically step up attacks on Shiites, whom they regard as apostates.
The deadliest unrest was on the outskirts of Baquba, which lies north of Baghdad and is one of Iraq's most violent areas, with three coordinating bombings targeting a gathering of Shiite pilgrims marking Ashura.
The blasts killed at least eight people and wounded 25, security and medical officials said.
In the days leading up to the climax of Ashura, which this year falls on Thursday, Shiite Muslims often set up procession tents where food is distributed to passers-by and pilgrims can gather.
Other worshippers walk to Karbala, which is home to a shrine to Imam Hussein, whose death in 680 AD at the hands of the caliph Yazid has over time come to mark the symbolic split between Islam's Sunni and Shiite sects.
Sunni militants linked to Al-Qaeda, who regard Shiite Muslims as unbelievers, often step up their targeting of Iraq's majority community during Ashura and the subsequent rituals of Arbaeen.
Violence elsewhere in Iraq on Wednesday killed 10 people and police also gunned down three militants, officials said.
East of the predominantly Sunni Arab town of Tikrit, a suicide bomber detonated a vehicle rigged with explosives at a police checkpoint, killing six people - three policemen and three civilians.
And near the former insurgent bastion of Fallujah, two bombs targeting the homes of policemen, followed by a third that went off as onlookers gathered at the scene, killed four people and wounded a dozen more overall.