Multiple blasts were targeted at a school in the Afghan capital Kabul on Saturday killing at least 40 people and wounding dozens more, mostly students, a senior interior ministry official has said.

The ministry spokesman, Tariq Arian, said at least 52 people were injured in the blast in the Afghan capital. He did not specify the cause of the explosion.

The official told Reuters on condition of anonymity that most of the casualties were students coming out of the Sayed ul Shuhada school.

Ghulam Dastagir Nazari, a spokesman for the health ministry, said 46 people had been taken to hospitals so far.

Kabul is on high alert since the US president, Joe Biden, announced plans last month to pull out all US troops by the 20th anniversary of the September 11 attacks, with Afghan officials saying Taliban have stepped up their attacks across the country.

No group has claimed responsibility for Saturday’s blast.

The attack took place in the west of Kabul, a heavily Shia Muslim neighbourhood that has frequently been attacked by Islamic State militants over the years.

The school is a joint high school for girls and boys, who study in three shifts, the second of which is for female students, Najiba Arian, a spokeswoman for the Ministry of Education, told Reuters. The wounded are mostly female students, she said.

“The horrendous attack in Dasht-e-Barchi area in Kabul, is a despicable act of terrorism,” the European Union’s mission in Afghanistan said on Twitter. “Targeting primarily students in a girls’ school, makes this an attack on the future of Afghanistan.”