- Video report by ITV News Security Editor Rohit Kachroo
At least 41 people have been killed and a further 84 wounded after gunmen stormed a Shiite Muslim cultural centre in Kabul and set off several bombs, authorities said.
Interior Ministry spokesman Najib Danish said an unknown number of suicide attackers set off an explosion outside the centre before storming the building.
They then set off explosive devices in the basement of the building, where scores of people had gathered to mark the December 1979 invasion of Afghanistan by the former Soviet Union, he said.
Shiite leader Abdul Hussain Ramazandada said witnesses reported at least one suicide bomber slipped into the event and was sitting among the participants.
He exploded his device, and as people fled more explosions occurred.
The centre is located in the Shiite-dominated Dasht-e-Barchi neighborhood in the west of the capital.
The Islamic State group affiliate in Afghanistan has claimed responsibility for the blast.
As attacks targeting Shiites have increased in Kabul, residents of this area have grown increasingly afraid. Most schools have additional armed guards from among the local population.
Still, Mr Ramazandada said security at the cultural centre was light.
The IS affiliate in Afghanistan is made up of Sunni extremists and views Shiites as apostates.
The terror cell is largely made up of a mix of Uzbek militants belonging to the Islamic Movement of Uzbekistan who broke with the Taliban, as well as disenchanted insurgents who left the much larger and more well-established Taliban.
Afghan president Ashraf Ghani called the attack a "crime against humanity".
In a statement released by the presidential palace, Ghani said: "The terrorists have killed our people.
"The terrorists have attacked our mosques, our holy places and now our cultural centre."
He called them attacks against Islam and "all human values".
The British Foreign Secretary Boris Johnson also spoke out, saying that the UK stood with Afghanistan against terror.
"I am appalled by this despicable attack on a cultural centre in Kabul which has claimed so many innocent lives, and my heartfelt condolences go out to the victims and their families," he said.
"Initial reports suggest that Daesh in Afghanistan have claimed responsibility. The disregard for humanity shown today bears all the hallmarks of their hateful ideology which must be countered wherever it is found."
The White House said President Donald Trump has been briefed on the attack, and the President is continuing to monitor the situation.
The blast came days after another attack that killed six shepherd children on Wednesday.
Dawlat Abad District Governor Mohammad Karim said the earlier powerful mine blast killed children ranging in age from eight to 10.
No one immediately took responsibility for the attack but Karim blamed the Taliban, saying the insurgents planted the mine to target Afghan officials and security forces.
Afghanistan has the highest number of mine victims in the world, which along with other roadside bombs, kill or wound an estimated 140 people every month.
Elsewhere, a Taliban attack on a security police post in central Ghazni province Wednesday night left three police dead and one other wounded, said Mohammad Zaman, provincial chief of police.