Militants fired mortar bombs at the gathering on Thursday, a commemoration on the anniversary of the death of a leader of the Hazara ethnic minority.
Hundreds of people including top government officials such as Chief Executive Officer Abdullah Abdullah and at least three candidates for a July presidential election were at the event.
Nasrat Rahimi, spokesman for the ministry, said in a statement 95 people were wounded in what officials initially described as a rocket attack.
Rahimi said the Taliban planned the attack. On Thursday, the Islamic State militant group said it was responsible.
Sunni Muslim militants, including the Taliban and Islamic State, have repeatedly attacked Hazara people in Afghanistan and neighboring Pakistan over the years.