A car bomb targeted Shia pilgrims in an area near Baghdad on Saturday, killing at least 14 people and wounding at least 25, security and medical officials said.
The bomb was left on a road in the Nahrawan area used by Shia pilgrims who are walking to the shrine of Imam Musa Kadhim in northern Baghdad for annual commemorations.
Kadhim, the seventh of 12 imams revered in Shia Islam, died in 799 AD. The commemoration has in recent years turned into a huge event that brings the Iraqi capital to a standstill for days.
There was no immediate claim of responsibility for the attack, but the Islamic State militant group frequently targets members of Iraq's Shia majority, whom it considers heretics.
Last year's pilgrimage was also marred by attacks against worshippers that killed at least 13 people.
And four more were burned or shot to death when mobs torched houses and a Sunni religious endowment building after rumours of a suicide bomber sparked panic among a crowd of pilgrims.
IS group overran large areas north and west of Baghdad in 2014, but Iraqi forces backed by US-led military assistance have since regained significant ground.
The Islamist militants still control a large part of western Iraq, and are able to carry out frequent attacks against both civilians and security forces in government-held areas.