A bomb tore through a university preparatory academy in Kabul, killing 48 and injuring 67 others, according to the country’s Health Ministry.
The attacker targeted the private school in the minority Hazara neighborhood where a group of young men and women were studying for university entrance exams.
The Taliban denied involvement in the attack, and there was no immediate claim of responsibility. Islamic State extremists have in the past targeted Shiite Muslim Hazaras, who they consider apostates.
Jawad Ghawari, a senior Shiite cleric, blamed the ISIS. There have been at least 13 attacks on the Shiite community in Kabul alone, he said.
The bloodshed in Kabul capped off a grim few days throughout Afghanistan.
Also on Wednesday in eastern Laghman province, six girls gathering firewood were killed when they found an unexploded rocket shell, according to a local official.
A spokesman for the governor of Laghman, Sarhadi Zwak, said the victims were aged between 10 and 12. He blamed insurgents rockets for the deaths.