A car bomb has killed at least 13 Shi'ite pilgrims in Baghdad on the anniversary of the death of a revered 8th century religious leader.
Police and medical sources say at least 28 others, including women and children, were wounded.
A parked car containing explosives detonated Monday in the southwestern Saydiyah neighborhood, as Shi'ite Muslims conducted an annual pilgrimage to Imam Moussa al-Kadhim's shrine in northern Baghdad.
There was no immediate claim of responsibility, but such attacks have been carried out in the past by Islamic State.
IS executed a similar attack that killed 23 pilgrims on Saturday on the outskirts of the Iraqi capital.
Tens of thousands of Shi'ite pilgrims have been traveling for days to northern Baghdad, where the imam is buried.
In recent years, the pilgrimage has drawn more visitors to Baghdad, bringing the capital to a standstill for days.
The main event at the shrine will take place on Tuesday.
Security forces have blocked major roads in Baghdad in anticipation of attacks.