Throngs of Shiite Muslims converged on a shrine in Baghdad on Saturday for an annual ritual under heavy security, but a string of attacks outside the capital killed 25 people.
The bloodshed was the latest in a protracted surge in nationwide unrest that has fuelled fears Iraq is slipping back into the all-out communal conflict that plagued it in 2006 and 2007, leaving tens of thousands dead.
Much of Baghdad was on lockdown Saturday for the climax of the rites to mark the death of a revered figure in Shiite Islam, with Baghdad's security forces looking to deter Sunni militant groups which often target Iraq's majority community.
Several major roads were closed off and a wide variety of vehicles barred from the streets, as security forces also relied on aerial cover and sniffer dogs.
Organisers say millions of pilgrims are expected to visit the shrine in the Kadhimiyah neighbourhood of north Baghdad between Saturday and Sunday, when the commemoration rituals are to climax.
For days worshippers from across the country, have been walking to Kadhimiyah, site of a shrine dedicated to Imam Musa Kadhim, the seventh of 12 revered imams in Shiite Islam, who died in 799 AD.
Sunni militants regard Shiites as apostates and, as in previous years, multiple attacks have targeted worshippers in the run-up to the annual commemoration.
Three bombings in the capital, including two carried out by suicide attackers, on May 22 killed 21 people, while mortar fire on Friday struck a district adjacent to Kadhimiyah, killing three more.
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Outside of Baghdad on Saturday, a series of attacks killed 25 people, security and medical officials said.
In the deadliest attack a car bomb exploded outside an alcohol shop in the northern city of Kirkuk, killing 10 people and wounding 33 others.
In Kirkuk province three farmers kidnapped in the early hours of the morning were found beheaded.
Another vehicle rigged with explosives, this time set off by a suicide attacker, targeted an army convoy in Diyala province escorting Iranian workers who had been installing a gas pipeline between Iran and Iraq.
Five people were killed -- three Iranians and two soldiers -- and 13 people were wounded, including eight Iranians.
Attacks also struck in the restive provinces of Nineveh and Salaheddin, officials said.
Violence has surged in the past year to its highest level since 2008, while anti-government fighters also control an entire city a short drive from Baghdad and parts of another.
The authorities have trumpeted security operations against militants, claiming to have killed around 90 on Saturday alone, and blame external factors such as the civil war in neighbouring Syria for the surge in violence.
Analysts and diplomats, however, say the Shiite-led government must also do more to reach out to disgruntled minority Sunnis and undermine support for militancy.