A British IS fighter who died in a suicide bomb attack on Iraqi forces in Mosul is a former Guantanamo Bay detainee, the BBC understands.
The self-styled Islamic State group said two days ago that Abu-Zakariya al-Britani detonated a car bomb at an Iraqi army base in Tal Gaysum, south-west of Mosul.
He is believed to have been originally known as Ronald Fiddler.
Fiddler, 50 and from Manchester, was sent to Guantanamo Bay in 2002.
He had been seized by US forces in Afghanistan, and was released just over two years later.
IS has now published a photograph of Fiddler, who was also known as Jamal al-Harith before taking the name Abu-Zakariya al-Britani.
The BBC has seen IS registration papers signed by Fiddler in April 2014 when he crossed into Syria from Turkey.
He volunteered to be a fighter, saying his knowledge of Islam was basic.
According to figures published by the UK government last year, about 850 people regarded as a national security concern have gone to become fighters in the Middle East.
Of those, just under half have returned to the UK and approximately 15% are dead.
A Foreign Office spokeswoman said: “The UK has advised for some time against all travel to Syria, and against all travel to large parts of Iraq.
“As all UK consular services are suspended in Syria and greatly limited in Iraq, it is extremely difficult to confirm the whereabouts and status of British nationals in these areas.”