A bomber blew himself up on Friday at a Kabul study hall as hundreds of pupils were taking tests in preparation for university entrance exams in the city's Dasht-e-Barchi area.
The western neighbourhood is a predominantly Shiite Muslim enclave and home to the minority Hazara community - a historically oppressed group that has been targeted in some of Afghanistan's most brutal attacks in recent years.
Police said at least 20 people were killed but the United Nations mission in Afghanistan considers the number to be higher, with at least 35 fatalities and an additional 82 wounded.
On Saturday about 50 women chanted, "Stop Hazara genocide, it's not a crime to be a Shiite", as they marched past a hospital in Dasht-e-Barchi where several victims of the attack were being treated.
Dressed in black hijabs and headscarves, angry protesters carried banners that read: "Stop killing Hazaras", an AFP correspondent reported.
Witnesses have told AFP that the suicide attacker detonated in the women's section of the gender-segregated hall.
"Yesterday's attack was against the Hazaras and Hazara girls," protester Farzana Ahmadi, 19, told AFP.
"We demand a stop to this genocide. We staged the protest to demand our rights."
Protesters later gathered in front of the hospital and chanted slogans as dozens of heavily armed Taliban, some carrying rocket-propelled-grenade launchers, kept watch.
Since the hardline Taliban returned to power last August, women's protests have become risky, with numerous demonstrators detained and rallies broken up by Taliban forces firing shots in the air.
No group has claimed responsibility for Friday's attack at the Kaaj Higher Educational Centre.
But the jihadist Islamic State (IS) group regards Shiites as heretics and has previously claimed attacks in the area targeting girls, schools and mosques.
The Taliban also regard the Hazara community as heathens, and rights groups often accused the Islamists of targeting them during their 20-year insurgency against the former US-backed government.
Since returning to office the Taliban have pledged to protect minorities and clamp down on security threats.
However, rights group Amnesty International said Friday's attack was "a shamefaced reminder of the inaptitude and utter failure of the Taliban, as de-facto authorities, to protect the people of Afghanistan".
In May last year, before the Taliban's return to power, at least 85 people — mainly girls — were killed and about 300 were wounded when three bombs exploded near their school in Dasht-e-Barchi.
No group again claimed responsibility, but a year earlier IS claimed a suicide attack on an educational centre in the same area that killed 24.
IS has emerged as a key security challenge for the Taliban, but officials claim their forces have defeated the jihadists.
Some victims of terrorist attack on Kaaj educational centre in Kabul. Around 60 Hazara girls were killed and tens of others wounded. It sparked worldwide #StopHazaraGenocide campaign. (RAWA.org)