LONDON • They called him Abu Zakariya al-Britani - the surname means "the Briton" - and they said he blew himself up on Monday in an attack at a village south-west of Mosul, Iraq.
The claim, made in a communique from the Islamic State in Iraq and Syria (ISIS), immediately revived fears of foreign fighters who have moved to Syria or Iraq to join the group's ranks.
In Britain, it prompted even more troubling allegations.
Several British news organisations - including the BBC, The Times of London and The Guardian - reported on Tuesday that the man was Jamal Malik al-Harith, a native of Manchester, England, who was captured in Afghanistan in 2001; detained by the United States in the military prison at Guantanamo Bay, Cuba, from 2002 to 2004; and released to Britain, where the government later awarded him £1 million (S$1.76 million) to settle a lawsuit.
The possibility that a former Guantanamo inmate had gone to Iraq to blow himself up stirred outrage in British tabloids.
He was in this country, and he was able to leave and fight for ISIS, and that raises questions on border checks. That said, he had lain low so attention was put on people who were more active.
LORD ALEX CARLILE, a lawyer who was an independent reviewer of Britain's terrorism legislation from 2001 to 2011, on al-Harith.
It also prompted an emphatic response on Wednesday from former prime minister Tony Blair, whose decision to join then US president George W. Bush in invading Iraq in 2003 remains divisive.
Mr Blair said in a statement that he was being unfairly blamed for the Americans' release of al-Harith to Britain, even though it was widely supported at the time.
"It is correct that Jamal al-Harith was released from Guantanamo Bay at the request of the British government in 2004," Mr Blair said.
"This followed a massive media and parliamentary campaign, led by The Daily Mail, the very paper that is now supposedly so outraged at his release, and strongly supported by the then Conservative opposition."
Mr Blair added that the compensation was agreed to in 2010 by the government of the Conservative prime minister David Cameron.
The terrorist group ISIS released a photograph of a militant it said was the bomber. The Times of London quoted a man named Leon Jameson as saying that the person in the photograph was his brother, al-Harith. However, neither American nor British officials verified that the militant was al-Harith, who was also known as Ronald Fiddler.
According to Defence Department documents, he was born in 1966 in Manchester. He was detained by the Taleban in Pakistan.
He was then held by the Taleban in Kandahar, Afghanistan, where he was detained by United States forces in October 2001.
He was transferred to Guantanamo Bay in February 2002. That September, Major-General Michael Dunlavey, who was in charge of intelligence operations at Guantanamo, recommended that al-Harith be approved for release or transfer, based on an assessment that he "was not affiliated with Al-Qaeda or a Taleban leader".
Nonetheless, Pentagon officials had their doubts about the man. They noted that he had travelled extensively in the Middle East from 1992 to 1996, and that he had joined an Al-Qaeda operative who went to Sudan in 1992 at the same time that Osama bin Laden was active there.
On Wednesday, lawyer Alex Carlile, a member of the House of Lords who served as an independent reviewer of terrorism legislation in Britain from 2001 to 2011, said "it is absolutely plain and clear that he had significant radical associates".
He added: "He was in this country, and he was able to leave and fight for ISIS, and that raises questions on border checks.
"That said, he had lain low so attention was put on people who were more active."
NEW YORK TIMES