At least 43 people have been killed after a suicide bomber attacked a gathering of religious scholars in the Afghan capital, Kabul, officials say.
Other 83 people were also wounded as the clerics met at the Uranus wedding hall, a large banqueting complex near the airport, to mark the birthday of the Prophet Muhammad.
The attack is one of the deadliest in Kabul in recent months.
No-one has yet admitted responsibility for the blast.
Some 1,000 people were said to be in the complex at the time of the attack.
The suicide bomber gained entry and headed for the centre of the gathering, where he detonated his explosives.
Religious studies lecturer Mohammad Hanif said there was a deafening explosion and “everyone in the halls was screaming for help”.
1TV News quoted the health ministry as saying that 24 of the wounded were severely injured.
Afghan President Ashraf Ghani condemned the “terrorist attack”.
The president declared November 21 a day of national mourning, with the flag to be flown at half mast.
The UN mission in Afghanistan tweeted: “UNAMA outraged by #Kabul bombing when communities across #Afghanistan are marking day of special religious significance. Credible reports of heavy civilian casualties. UN human rights teams establishing facts. UN family extends deepest condolences to the many families affected.”
Pakistan’s PM Imran Khan condemned the “cowardly act of terrorism” and sent his condolences to the bereaved families.
The Islamic State in Afghanistan group, sometimes known as Islamic State Khorasan, has claimed responsibility for most of the recent deadly attacks of this kind.
It said it was behind two attacks in Kabul in August that killed dozens of people.
The Taliban have also continued attacks, although many of them target security forces.
A Taliban spokesman, Zabiullah Mujeed, has denied the group had any involvement in November 20 attack.