So-called Islamic State (IS) has said it was behind Saturday's attack on members of the Shia Hazara minority.
In a televised address, President Ashraf Ghani vowed to take revenge against those responsible.
The UN mission in Afghanistan has described the attack as a "war crime".
Tadamichi Yamamoto, head of the UN assistance mission, said the attackers had specifically targeted a large number of civilians.
On Saturday, the IS-linked Amaq news agency said two fighters had detonated explosive belts at a "gathering of Shia" in Deh Mazang square.
