The United Nations Assistance Mission in Afghanistan (UNAMA) has raised the death from a suicide bombing at an education center in Kabul to 40.

Afghan authorities initially reported 48 were killed in the August 15 attack but revised the number down to 34.

But in a statement on August 18, UNAMA said it had verified that 40 students were killed and 67 wounded after a suicide bomber detonated his explosives inside a classroom in the Mawoud Academy in Dasht-e Barchi, a predominately Shi’ite neighborhood in western Kabul.

“An attack deliberately targeting students can only be described as a cowardly act of terror,” said Tadamichi Yamamoto, the UN secretary-general's special representative for Afghanistan and the head of UNAMA, in a statement on August 18.

“This atrocity not only robbed these young women and men of their futures but also deprived Afghanistan of all the benefits that their education and potential would have brought this country,” he added.

The Islamic State (IS) extremist group claimed responsibility for the attack.

IS extremists have carried out similar attacks in the past, hitting Shi'ite mosques, schools, and cultural centers.