More than 46 people were killed with more wounded in a suicide bomb attack at a mosque in the provincial capital city of Kunduz in Afghanistan on Friday, officials said.

Officials weren’t sure exactly how many died in the blast or who was responsible. The crowd that suffered the attack were doing their prayers.

The United Nations (U.N.) Assistance Mission in Afghanistan said initial reports indicate the dead and wounded numbers.

“Today’s incident is part of a disturbing pattern of violence,” the U.N. mission said in a tweet. “[It was the] third deadly attack this week apparently targeting areligious institutions.”

Zabiullah Mujahid, deputy minister of information and culture, told TOLO News that the bombing targeted a mosque attended by Shia Muslims.

Ahmadullah Wasiq, the Taliban’s deputy head of the Cultural Commission of the Ministry of Information and Culture, said security forces arrived at the scene after the attack to investigate.

No group immediately claimed responsibility for the attack, but the rival ISIS-K militant group has launched similar attacks against the Taliban in the past — including one that killed more than a dozen U.S. Marines during the evacuation in Kabul in August.