At least 43 people were killed in a suicide bombing at a meeting of top clerics in Kabul on Tuesday, officials said, in one of the deadliest attacks to strike Afghanistan this year.

It follows a wave of bloody violence across the war-torn country in recent weeks, with hundreds of people killed as militants step up assaults amid a flurry of diplomatic efforts to end the 17-year conflict.

At least 83 people were wounded in the blast, health ministry spokesman Wahid Majroh said, which targeted religious leaders inside a wedding hall where hundreds had gathered to mark the Prophet Mohammad's birthday. At least 24 are in a critical condition.

A photo posted on WhatsApp purportedly of the function room showed blood splattered bodies, some with the clothes partially ripped off by the force of the blast, overturned chairs and broken glass strewn over the floor.

"The suicide bomber detonated himself inside the hall during a ceremony involving religious scholars," Kabul police spokesman Basir Mujahid said, confirming the casualty toll.