Witnesses told the BBC a suicide bomber detonated explosives during a wedding ceremony.
The explosion happened at around 22:40 local time (18.10 GMT) in an area in the west of the city mostly populated by Shia Muslims.
The Taliban denied it was behind the attack. No other group has admitted carrying out the bombing.
Sunni Muslim militants, including the Taliban and the Islamic State group, have repeatedly targeted Shia Hazara minorities in Afghanistan and Pakistan.