The attack took place during Friday prayers at the Sayed Abad mosque in Kunduz, provincial spokesman Matiullah Rohani told CNN.
At least 20 people were killed and 90 injured, according to Sara Chare, an MSF official who said some of the injured had been taken to the NGO’s facility.
A Taliban spokesman said security forces were on the scene and an investigation was underway.
ISIS-K claimed responsibility for the blast, according to a statement released by the group’s media wing, Amaq. It added that a suicide bomber blew up his explosive vest among Shia worshipers inside a mosque during Friday prayers in the Khan Abad district of the northern Afghan city of Kunduz.
Friday’s mosque bombing “is part of a disturbing pattern of violence” and the third deadly attack this week “apparently aimed at a religious institution,” the United Nations Mission in Afghanistan (UNAMA) said on Twitter.
Islamic State-affiliated company IS Khorasan (ISIS-K) claimed responsibility for Monday’s bombing, one of a series of attacks launched by the terrorist group since the Taliban took control of Afghanistan more than a month ago. Others include a suicide attack at Kabul airport in August and a stream of bombings against members of the Taliban in the eastern Afghan city of Jalalabad.
The group poses a threat to the country’s stability and the Taliban’s rule. In recent days, the Taliban have carried out several operations targeting ISIS-K militants.
The Taliban claimed to have killed at least nine ISIS K members and detained five others in two operations last week, targeting ISIS hideouts in the central Afghan province of Parwan, according to local Taliban police chief Maulvi Abdul Qadir Haqqani.