The blast targeted a political party gathering in the town of Khar in Bajaur district. More than 200 people were wounded.
The Takfiri terrorist group announced in a statement issued on its news arm Ama that a bomber from Daesh “detonated his explosive jacket in the middle of a crowd.”
Virtually 1,000 people had gathered under a large tent as their party prepared for parliamentary elections due later this year.
Parliament is likely to be dissolved after it completes its term in the next two weeks with national elections to be held by mid-November or earlier.
The administration of Prime Minister Shehbaz Sharif has vowed to hunt down those responsible for the bombing.
A spokeswoman for the EU foreign policy chief Josep Borrell has said what happened in Pakistan was “a terrible attack” that sought “to instill terror.”