At least 10 people died and "many more" were injured in a blast at a madrasa -- a religious school -- in Aybak, northern Afghanistan, on Wednesday, according to the Taliban.
But doctors at a local hospital put the death toll much higher, saying at least 19 people are dead and 24 others wounded.
The explosion went off at the Al Jihad madrasa in Aybak at around the same time as students would have been gathering for afternoon prayers.
Most of the victims, who have not yet been identified by authorities, were "children and ordinary people," the doctor told AFP under the condition of anonymity.
The BBC, citing local sources, said the children were aged between 9 and 15.
Footage and pictures from the scene of the blast distributed by the Taliban showed broken glass, debris and traces of blood in the room where bodies are strewn on the floor.
The attack is the latest of a series of explosions that have targeted civilians in Afghanistan since the return of the Taliban to power in August 2021, after the hasty withdrawal of American troops from the country. On 30 September, a suicide attack at a Kabul hall packed with students preparing for university admissions killed 54 people, including 51 girls, according to the UN.
A few days later, on 5 October, at least four people were killed in an explosion at a mosque in Kabul during the Muslim holy month of Ramadan.
Most of the attacks have been claimed by the local branch of the Islamic State, known as Islamic State - Khorasan Province (ISIS-K). The group is known to target religious minorities -- like the Hazars --, the same people the Taliban have promised to protect.
Wednesday's blast has not yet been claimed by any group in Afghanistan, but the government has accused ISK of being responsible.
"Our detective and security forces are working quickly to identify the perpetrators of this unforgivable crime and punish them for their actions," tweeted Interior Ministry spokesman Abdul Nafay Takor on Wednesday.