Afghanistan was marking a day of national mourning on Sunday after 80 people were killed and an estimated 231 were wounded in a bomb attack during a demonstration in Kabul.
Two attackers detonated their suicide vests among a crowd of protesters, while another was killed by security forces.
At least 10,000 people were taking part in the protest, according to event organizer Mohammad Arif Rahmani.
Most of the protesters were Hazaras, a Shiite minority from central Afghanistan, who have long suffered discrimination, especially under Taliban rule when thousands from the tribe were killed.
The Hazara minority ethnic group makes up 22 per cent of Afghanistan's Sunni-dominated population.
They were demanding that a new power cable being laid from Turkmenistan to Pakistan via Kabul be rerouted through the province of Bamyan, currently not connected to the electricity grid.
The government has rejected the demands, citing further delays and added costs.
The Islamic State extremist group claimed responsibility for the bombing.
Islamic State has been known to carry out brutal attacks against Shiites in Iraq and Syria, but this is the first attack they have claimed in Kabul against an ethnic minority.
Abdullah, 23, told dpa on Sunday that he was in the area when the bomb went off. "I was sitting behind a vehicle that blocked the blast, otherwise I would be dead," he said.
"It was horrific, one of the worst experiences of my life," he recalled.
"We were there to ask for ... justice, but instead we got blown up," he added.
One analyst remained sceptical about Islamic State's role in the bombing.
"I don't think Islamic State carried out the attack at all," said analyst Ahmad Saeedi, adding that the militant group mostly active in eastern Afghanistan is "not powerful enough to plan such a huge attack in the capital."
He blamed the government for the incident and for failing to secure the area where the protest took place.
"Political opposition between the organizers and other parties created such a scene," said Saeedi.
President Ashraf Ghani vowed to "avenge the blood of our loved ones," and ordered the flag to fly at half-mast at all government buildings in Afghanistan and abroad.
The Interior Ministry announced a nationwide 10-day ban on protests due to security reasons after the attack.