As many as 21 people were killed and 33 injured in a huge explosion in a mosque in Kabul during evening prayers on Wednesday, police and witnesses said.
The bombing in the Afghan capital killed a prominent cleric and wounded several children, officers said.
There was no immediate claim of responsibility for the attack.
Witnesses said a powerful explosion was heard in a north-west Kabul neighbourhood, shattering windows in nearby buildings.
One witness said that a suicide bomber was responsible.
“A blast happened inside a mosque … the blast has casualties but the numbers are not clear yet,” said Kabul police spokesman Khalid Zadran.
Italian medical non-government organisation Emergency said it had received 27 casualties from the blast, including three fatalities.
A Taliban intelligence official said the explosion had occurred in a mosque in the Khair Khana area.
The imam of the mosque was among those killed and the death toll could still rise, the source said. Intelligence teams were at the blast site and investigations were ongoing.
Other officials in the Taliban government did not reply to requests to confirm the number of casualties.
Taliban spokesman Zabihullah Mujahid condemned the bombing and vowed to punish the perpetrators and bring them to justice.
A local affiliate of ISIS has recently ramped up its attacks, targeting Taliban fighters and civilians — particularly from the Shiite Hazara minority — since the Taliban took over the country last August.
In another attack last week, ISIS said it was responsible for killing a well-known Taliban cleric in Kabul.
Since their rise to power, the Taliban have been grappling with an economic crisis, especially as the international community froze most aid funding and cut access to Afghanistan's foreign reserves.
In a separate incident, the Taliban said on Wednesday that they had captured and killed a rebel Shiite minority opposition member from the Hazara community.
Mehdi Mujahid had recently rebelled against the Taliban, in opposition to decisions the group had taken in Kabul.
He was caught in Balkhab district, in Sar-e Pol Province, in northern Afghanistan, the Taliban said.