* Funerals begin for more than 80 killed in suicide attack
* Islamic State claims attack on mainly Shi'ite Hazaras
* Fury at political leaders (Releads with funerals, adds detail, background)
By Mirwais Harooni
KABUL, July 24 (Reuters) - Members of Afghanistan's Hazara minority began the task of burying more than 80 people killed in Saturday's suicide attack in Kabul with many blaming political leaders for security failures that led to the massacre.
Officials said 84 graves were dug into a hillside in the west of Kabul and bodies were brought up throughout the afternoon but, with large public assemblies banned for security reasons, there was no mass funeral.
The attack on Saturday, against a demonstration by the mainly Shi'ite Hazara, was among the worst in Afghanistan since the fall of the former Taliban regime in 2001.
It was claimed by Islamic State, which had never carried out any operation on a comparable scale in Afghanistan, raising fears of a new escalation and the kind of sectarian violence which has so far been relatively uncommon.
Earlier, relatives of some of those killed had searched through a bloodied assortment of belongings left after the twin blasts tore into a demonstration where thousands were protesting over the route of a planned power transmission line.
"Those are my cousin's sandals," said Sayed Mohammad as he stood in a crowd of people looking for anything familiar among the remnants spread out by authorities on an Afghan flag in the Dasht-e-Barchi area of Kabul.
"He was the only breadwinner of his family. I'm looking here if I can find anything more from other relatives."
President Ashraf Ghani announced a day of mourning and ordered Dehmazang Square, the site of the blasts, to be renamed Martyrs Square. As well as the more than 80 dead, some 230 people were injured.
The attack, described by the top U.N. official in Afghanistan as a "war crime", drew condemnation and offers of support from countries including Russia and the United States.
But for some, there was fury at both the government and Hazara political leaders.
The Hazara, a Persian-speaking minority who make up about 9 percent of the population, have long suffered discrimination and violence. They have by and large supported Ghani's government, which includes some of their senior leaders, but many complain their support has not been returned.
"They sold us and we will never forget this," said Ghulam Abbas, a Hazara mourner. "They've built skyscrapers for themselves and their families from our blood."
Reflecting the often unfocused anger that erupted after the attack, witnesses saw some demonstrators turning on police who arrived in the aftermath of the explosion and some even blamed the government for the attacks.
"If the Taliban and Daesh do not have helpers in the presidential palace, how can they carry out such attacks?" asked Taher Ahmadi from Waras district in Bamyan province, using the term generally used in Afghanistan for Islamic State. He said 15 people from his village were killed in the attack.
Saturday's protest over a multimillion dollar power line, which demonstrators wanted to re-route through two provinces with large Hazara populations, had become a touchstone for a wider sense of injustice.
The demonstration took place under tight security, with much of Kabul blocked off. But there was disagreement in the Hazara community as well as in the government about whether it should have gone ahead given the obvious risk of an attack.
For many, such as 42 year-old Dost Mohammad, who was nearby when the two explosions went off, there was a sense of abandonment by the authorities.
"With all this misery, the government doesn't care about its own citizens."
(Additional reporting by Sayed Hassib; Writing by James Mackenzie; Editing by Robert Birsel/Ruth Pitchford)
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