Tuesday's bombing of a Kabul shrine was part of a campaign to target Shia Muslims in Afghanistan, a man claiming to lead a new Afghan group says.
The man, who gave his name as Ali Sher-e-Khuda, told the BBC his group was inspired by Pakistan's Sunni militant Lashkar-e-Jhangvi organisation.
He said the group had not officially sanctioned the Kabul attack, but did not deny his men carried it out.
It has raised fears of a wave of new sectarian violence in Afghanistan.
Afghan officials say the attack was the work of Lashkar-e-Jhangvi, but they have cast doubt there is a new Afghan group active in the country with formal links to it.
The killing of at least 71 Shia worshippers earlier this week was the first significant sectarian attack in Afghanistan since the fall of the Taliban.
Despite suffering years of violence, the country has not seen the attacks between Sunni and Shia Muslims that have been common in Pakistan and Iraq.
'Fighting discrimination'
Ali Sher-e-Khuda spoke to the BBC's Shoaib Hasan at a secret location in the Pakistani border province of Balochistan.
He said his group - which he called Lashkar-e-Jhangvi Afghanistan - is relatively new and operated on both sides of the Pakistan-Afghan border.
He said the organisation was made up of Afghans who are targeting Afghanistan's Shia minority.
"I was born in Nimroz and am of Afghan Pashtun origin," he said.
" set up the organisation with other like-minded young men from Afghanistan. Most of them hail from the provinces around Bamiyan - especially Wardak and Ghazni provinces," he said.
Mr Sher-e-Khuda said Tuesday's bombing was about fighting discrimination by "Afghanistan's ruling Shia elite".
When challenged on the tactic of murdering dozens of innocent worshippers, the militant leader argued it was the only way to counter what he described as "criminal behaviour" by Shias - such as displaying Shia banners in Sunni areas.
Afghan President Hamid Karzai and others believe the attack was mounted by one the established militant groups based inside Pakistan.
"Our information and sources show that the Kabul attack was carried out by Lashkar-e-Jhangvi," Afghan intelligence agency spokesman Lutfullah Mashal said.
Our correspondent says Lashkar-e-Jhangvi is one of Pakistan's deadliest militant groups. As well as being blamed for the killing of thousands of Shias, it has also been linked to a string of high-profile attacks, including the 2002 murder of US reporter Daniel Pearl.
Afghan caution
Mr Mashal said that as far as the National Directorate of Security was concerned, there was no such group as Lashkar-e-Jhangvi Afghanistan.
He said the claim was a tactic by Pakistan's Lashkar-e-Jhangvi to create sectarian tensions as the shrine attack had failed in its goal "to create a rift between Sunnis and Shias" in Afghanistan.
The US ambassador to Afghanistan, Ryan Crocker, said it was not clear who carried out the attack.
"I served in Pakistan for three years, I know all about Lashkar-e-Jhangvi. I am totally unaware of any Afghan affiliate," he said. "I personally doubt very much that there is such a thing."
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