An explosion struck a mosque in northern Afghanistan for the duration of Friday prayers, police said, with eyewitnesses reporting dozens of casualties.

The blast hit Mawlavi Sikandar mosque north of Kunduz city, provincial police spokesman Obaidullah Abedi informed AFP.

“At the moment we have no details about the type of the blast or about casualties,” he said.

Images posted to social media which could not be immediately verified showed holes blown through the walls of the mosque.

A nurse at a nearby district hospital told AFP over the phone that between 30 to 40 casualties had been admitted from the blast.

“The people had gathered to worship in the mosque, and a blast happened,” an eyewitness also told AFP over the phone. “There were a lot of casualties, around 30 to 40 people were injured and killed.”

There was no official confirmation on the casualties from the incident.

It comes a day after the Islamic State group claimed a bomb attack at a Shiite mosque in the northern city of Mazar-i-Sharif that killed at least 12 worshippers and left 58 people injured.

They also claimed a separate attack in Kunduz city, which killed four people and wounded 18.

Earlier on Friday the Taliban authorities said they had arrested the IS “mastermind” of Thursday’s bombing at the mosque in Mazar-i-Sharif.

Since Taliban fighters seized manipulate of Afghanistan closing year after ousting the USA-subsidized authorities, the number of bombings has fallen however the jihadist and Sunni IS has endured with attacks — regularly towards Shiite objectives.

Taliban officers insist their forces have defeated IS, but analysts say the jihadist organization is a key protection mission.