Health Ministry spokesperson Wahid Majroh said four women and two children were among 41 killed. Several journalists and students who were attending the discussion forum also died. He added that 84 people were wounded.
The suicide bombing was followed by two more blasts near the building's main entrance, though all the casualties were from the initial attack, said Kabul police spokesperson Basir Mujahid.
He said that a militant detonated himself on the first floor of the building where the event was in progress, while the news agency office was located on the upper floor.
The floors of the centre were covered in blood as wailing survivors and relatives picked through the debris, while windows of the news agency were all shattered.
The Islamic State group said on its propaganda outlet Amaq that it had targeted the Shia centre which, it alleged, received support from Iran. The terror group said it killed 100 people and injured at least 120.
The Taliban had earlier issued a statement saying they were not involved.
Afghan President Ashraf Ghani's spokesman issued a statement calling the attack an "unpardonable" crime against humanity, and pledging to destroy the terrorist groups.
The US Ambassador John R. Bass condemned "the horrific and indiscriminate attack on civilians".
"We remain confident the Afghan government and people, supported by their friends and partners, will defeat those behind these terrible acts," he said.
The bloodshed follows an attack on a private television station in Kabul last month, which was also claimed by the Islamic State.
Since the end of NATO's combat mission in January 2015, the government has been steadily losing ground to insurgents and now controls only 57 per cent of the country, according to the US Special Inspector General for Reconstruction of Afghanistan.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)