A suicide bomb attack on a mosque in the Afghan city of Kunduz has killed at least 50 people, officials say, in the deadliest assault since US forces left.
Images on social media showed bodies and debris inside the mosque, used by the minority Shia Muslim community.
More than 100 people were injured in the blast in the northern city.
No group has said it was behind the attack, but Sunni Muslim extremists, including a local Islamic State group, have targeted the Shia community.
They consider Shia Muslims to be heretics.
IS-K, the Afghan regional affiliate of the Islamic State group that is violently opposed to the governing Taliban, has carried out several bombings recently, largely in the east of the country.
Zalmai Alokzai, a local businessman who rushed to a hospital to check whether doctors needed blood donations, described seeing chaotic scenes.
"Ambulances were going back to the incident scene to carry the dead," he told AFP news agency.
While there has been no claim of responsibility so far, this attack bears all the hallmarks of IS-K, the group that targeted Kabul airport in a devastating bombing in August.
The group has repeatedly targeted Afghanistan's Shia minority in the past, with suicide bombers striking at mosques, sports clubs and schools. In recent weeks, IS has also stepped up a campaign of attacks against the Taliban.
IS targeted a funeral prayer service attended by a number of senior Taliban leaders in Kabul on Sunday, and there have been a spate of smaller attacks in the eastern provinces of Nangarhar and Kunar, where IS previously had its stronghold.
Friday's attack, if it has been carried out by IS, would mark a grim expansion of their activities into the north of the country. The Taliban say they have arrested dozens of members of IS and are believed to have killed others suspected of links to the group, but publicly they have also played down the threat IS poses.
Many Afghans hoped that the Taliban's takeover would at least herald a more peaceful, if authoritarian, era. But IS represents a significant threat to the Taliban's promise of improved security.
The Taliban took control of Afghanistan as foreign forces withdrew from the country in August following a deal between the US and the Taliban, two decades after US forces removed the militants from power in 2001.