At least 41 people are dead and more than 80 wounded after a series of explosions rocked Afghanistan's capital Kabul on Thursday morning.
In a statement released by the presidential palace, Ghani says: "The terrorist have killed our people".
Afghan president Ashraf Ghani has called the attack on a Shiite Muslim cultural center in Kabul a "crime against humanity". CNN reports nearly 100 people were at the cultural center at the time for the anniversary of the Soviet invasion of Afghanistan.
Afghan Journalists Safety Committee recently reported a surge in attacks against journalists, with at least 73 cases recorded in 2017, an increase of 35 percent compared with 2016.
No-one has yet said they were behind the attack.
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In the assault on Thursday, one suicide bomber managed to enter the Shiite facility, the Tebyan cultural center and religious school, during a group discussion, and he detonated his explosive vest, said Sadiq Muradi, Kabul's deputy police chief. In August, 31 people were killed in a terrorist attack on a Shiite mosque in Herat, a city close to the Iran border.
Interior Ministry spokesman Najib Danish said an unknown number of suicide attackers set off an explosion outside the center before storming the building when they set of more explosives in the basement. He said one reporter at the agency had been killed and one injured.
The attack took place at about 10.30am local time.
"I have little doubt that this attack deliberately targeted civilians", said Toby Lanzer, acting head of the U.N. Assistance Mission in Afghanistan.
A spokesman for the USA military mission in Afghanistan, Resolute Support, said the "barbaric attack will not deter the unwavering resolve we have in supporting the Afghan National Defense and Security Forces in achieving peace and freedom for the people of Afghanistan".