Police and medics said a suicide bomber detonated an explosive vest in the middle of a Shia Muslim gathering in Baghdad, killing at least 31 people and injuring 50 others on Saturday.
The explosion occurred inside a tent filled with people partaking in Ashura rituals to mourn the killing of Prophet Mohammad's grandson Hussein in the 7th century.
The tent was set up in a crowded market in the city's northern al-Shaab district.
There was no immediate claim of responsibility for the attack, but Daesh terrorist group frequently carries out suicide bombings targeting Shia Muslims.
Daesh has claimed several recent bombings including one on October 9 that killed at least five people, and two more earlier in the month that left at least 10 dead. And two more Daesh-claimed bombings killed at least 17 people in Baghdad at the end of September.