LONDON — Schoolchildren were among those killed and injured in another series of deadly blasts in Afghanistan’s capital city, Kabul, Tuesday morning.

At least six people were killed and over ten injured, Khalid Zadran, acting spokesman of the Taliban Kabul police wrote on Twitter, adding that security forces were on the scene and an investigation was launched into the attack. Unofficial reports indicate a higher number of casualties.

No one has immediately claimed responsibility for Tuesday’s attack.

United Nations Assistance Mission in Afghanistan condemned the “heinous” attack in a tweet saying, “those responsible for the crime targeting schools and children must be brought to justice.”

United Nations envoy Deborah Lyons extended deepest sympathies to victims’ families and wished for a speedy recovery for the wounded, in the same tweet.

The blasts happened at the entrance of Abdul Rahim Shahid high school located in a Shia Hazara neighborhood of the city. Hazaras are an ethnic/religious group that has been the target of attacks in the past. Most of the previous attacks in the same neighborhood were claimed by ISIS affiliates. Tuesday’s blast was the first attack in this neighborhood after the Taliban takeover in August.

Shi’a Hazaras are historically the most discriminated ethnic minority group in Afghanistan and have long faced violence and discrimination, according to Minority Rights International. according to Minority Rights International.

Save the Children’s country director in Afghanistan, Chris Nyamandi, issued a statement condemning the attack.

“Save the Children calls for safe access to education at all times for children in Afghanistan and for perpetrators of grave violations against children to be held to account,” the statement reads.

Today’s blasts follow Pakistani military airstrikes in the eastern Afghanistan provinces of Khost and Kunar which killed 47 civilians, mainly women and children, and left many wounded.

ABC News’ Aleem Agha and Guy Davis contributed to this report.