At least 24 people were killed and dozens wounded in Saturday's suicide bomb attack outside an education centre in Kabul, Afghan officials now say.
The explosion at the private facility, which offers courses for students in higher education, occurred late in the afternoon, the interior ministry said.
The building in the predominantly Shia Muslim Dasht-e-Barchi area usually hosts hundreds of students.
The Islamic State (IS) group said it was behind the attack.
It did not provide any evidence to back up its claim issued via its usual social media outlets.
One of its members detonated an explosives vest among a gathering of Shias, it said, while using a disparaging term for the religious community.
The Shia community in Afghanistan has previously been targeted by Sunni Muslim extremists such as IS, which views the Shia practice of Islam as heretical.
Earlier, the Taliban denied involvement in the attack.
"A suicide bomber wanted to enter the education centre," interior ministry spokesman Tariq Arian said in a statement, AFP news agency reports.
The spokesman added that the attacker was spotted by security guards "after which he detonated his explosives in an alley".
One local resident, Ali Reza, told AFP that those killed and injured were students waiting to enter the facility. "I was standing about 100m from the centre when a big blast knocked me down," he said.
Afghanistan has seen a rise in violence in recent weeks - with most of the attacks carried out by the Taliban. The violence threatens to imperil peace talks between government forces and the Taliban in the Qatari capital, Doha.
Saturday's attack is not the first to target an education centre in the country.
Forty-eight people - many of them teenagers - were killed in August 2018 when a suicide bomber walked into a tuition facility and detonated a device while teaching was under way. The Islamic State group said it was behind that attack.
And in May, 24 women, children and babies were killed when unidentified gunmen entered a maternity ward at a hospital in Kabul and opened fire.
Earlier this week, 11 children and their prayer leader died an air strike on a religious school in the northern Afghan province of Takhar, according to local officials. The Afghan government disputed the account, saying the strike had killed Taliban fighters.