"The latest assessment of the attack shows at least 35 dead and 82 injured," the United Nations Assistance Mission in Afghanistan (Manua) said on Saturday.
The latest report released Friday evening by the Afghan police had reported 20 dead and 27 injured.
Friday morning a man blew himself up in a training center where students were preparing to take a university entrance exam.
According to a student on site at the time of the explosion, interviewed by AFP on Friday, "most of the victims are girls".
"Few boys were hit because they were at the back of the class and the suicide bomber entered through the front door where the girls were sitting," another student, Ali Irfani, said.
The explosion occurred in the Dasht-e-Barchi neighborhood in western Kabul, a predominantly Shia Muslim area where the Hazara minority live.
Saturday morning, about fifty young women defied the ban on assembly imposed by the Taliban to shout their anger. The young girls, dressed in a black headscarf, marched on the main road that crosses the district, shouting the raised point "Stop the genocide of the Hazaras".
Armed with placards on which one could notably read "It is not a crime to be Shiite", they headed for the hospital where several victims were transported.
The very many heavily armed Taliban deployed on the spot fired in the air several times to try to disperse them, AFP journalists heard.
The Dasht-e-Barchi district has been heavily hit in recent years and since the Taliban returned to power in August 2021. Several attacks have been claimed by ISIS, the regional branch of ISIS, which considers the Hazaras as heretics. The attack on Friday has not been claimed.
The Taliban also consider the Hazara community to be pagans, and human rights groups have often accused them of targeting them.
Since returning to power, the Taliban have pledged to protect minorities and counter security threats. However, the NGO Amnesty International said Friday's attack was "a shameful reminder of the Taliban's inability and utter failure" to protect the Afghan people.
Last May, at least 85 people, mostly girls, were killed and around 300 injured when three bombs exploded near a school in the same neighborhood, Dasht-e-Barchi.
No group claimed responsibility for the attack, but a year earlier, IS had claimed responsibility for a suicide attack against an educational center in the same area, which left 24 dead. IS has become a major security problem for the Taliban, who claim to have defeated the jihadists.