Islamic State has claimed responsibility for a suicide bombing on a peaceful protest in the Afghan capital on Saturday that killed at least 80 people and wounded more than 200.
This is the first time the extremist group has struck in Kabul, and was the deadliest attack to hit the city in 15 years of civil war.
The bomber struck at a demonstration by Afghanistan's Hazara ethnic community, who were marching for a major regional power line to be routed through their home province.
The Hazaras are Shiite Muslims while most Afghans are Sunnis.
Two suicide bombers had attempted to target the demonstrators, but one of them was shot by police before he could detonate his explosives, according to Haroon Chakhansuri, a spokesman for Afghan president Ashraf Ghani.
He said that three city district police chiefs were injured and another three security personnel were killed.
Road blocks that had been set up overnight to prevent the marchers accessing the city centre or the presidential palace hampered efforts to transfer some of the wounded to hospital, witnesses said.
Angry demonstrators sealed some of the area around the square, and prevented police and other security forces from entering. Some threw stones at security forces.
Outside hospitals, long queues formed as the public offered to donate blood.
The Afghan interior ministry said that the current death toll is 81, with 231 more wounded in the bombing.
IS claimed responsibility for the attack in a statement issued by its news agency, Aamaq.
IS has had a presence on Afghanistan's eastern border with Pakistan, mainly in Nangarhar province, for the past year, but this is the first time the extremist group has struck the Afghan capital.
The bombing raises concerns over IS's growing capabilities in Afghanistan.
A surge in the number of attacks worldwide linked to Islamic State has been seen as an attempt to distract from a string of battlefield losses suffered by the extremists in Syria and Iraq, where the borders of their self-styled caliphate are shrinking.
Mr Ghani has announced a forthcoming military offensive in Nangarhar, expected to start within days, aimed at eliminating IS from the country.
He declared Sunday a day of national mourning and ordered a commission be set up to investigate the incident and described the attack as a clear effort to divide Shiites and Sunnis.