The blast in Muqdadiyah, which was hit by revenge attacks on homes and mosques after a January suicide bombing, also wounded at least 40 people.
The bombing targeted a funeral for a well-known member of the Beni Tamim, one of the main tribes in Diyala province, where Muqdadiyah is located, officials said.
There was no immediate claim of responsibility for the attack, but suicide bombings are a tactic almost exclusively employed in Iraq by the Islamic State group.
The Muqdadiyah attack came a day after bombings in a Shia area of northern Baghdad killed at least 39 people and wounded at least 76, the deadliest attacks in the capital so far this year.
Twin suicide bombing kills 70 in Baghdad's deadliest attack this year
IS, an extremist group, said in an online statement that two of its suicide bombers carried out the Baghdad attacks.
IS also claimed bombings at a cafe in Muqdadiyah killed at least 20 people and wounded dozens in January, after which revenge attacks targeted Sunni properties in the area.
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