A suicide bomber targeted a gathering of Muslim religious scholars in the Afghan capital on Tuesday, killing at least 43 people, officials have said.
Public Health Ministry spokesman Wahid Majroh said another 83 people were wounded in the Kabul attack, which took place as Muslims around the world marked the birthday of the Prophet Mohammed.
He added that more than 20 people are in a critical condition and that the toll could rise.
The suicide bomber was able to sneak into a wedding hall in Kabul where hundreds of religious scholars and clerics had gathered to mark the occasion, Interior Ministry spokesman Najib Danish said.
No one immediately claimed the attack, but both the Taliban and a local Islamic State affiliate have targeted religious scholars aligned with the government in the past.
"The victims of the attack unfortunately are all religious scholars who gathered to commemorate the birthday of Prophet Muhammad," said Basir Mujahid, spokesman for the Kabul police chief.
He said police had not been asked to provide security for the event, and that the bomber had easily slipped into the hall. Most wedding halls have private security.
Mohammad Muzamil, a waiter at the wedding hall, said he had gone into the back to fetch water for the guests when he heard the explosion.
"Everything was covered with smoke and dust," he said. "There were dead bodies all around on the chairs, in large numbers."
Police sealed off roads leading to the scene of the attack and ambulances could still be seen going in. Hundreds of family members and relatives gathered at local hospitals, looking at lists of those killed and wounded that were posted outside.
IS claimed a suicide bombing in June that targeted a meeting of the country's top clerics in the capital.
That attack killed at least seven people and wounded 20.
The body of religious leaders targeted in June, known as the Afghan Ulema Council, had issued a decree against suicide attacks and called for peace talks.
IS said it had targeted "tyrant clerics" who were siding with the US-backed government.
The Taliban denied involvement in the June attack but they also denounced the gathering.
Both militant groups want to overthrow the US-backed government and impose a harsh form of Islamic rule, but they are bitterly divided over leadership and ideology, and they have clashed on a number of occasions.
Additional reporting by Associated Press.
