A Welsh man who left the UK at 17 as one of the first British recruits to join the Islamic State group has been found in a secret prison in northern Syria, where up to 5,000 inmates are living packed into tiny cells.

Aseel Muthana left his job as an ice-cream salesman in his Cardiff hometown in 2014 to follow his brother to Syria.

Mr Muthana’s brother Nasser was a prominent recruiter for Islamic State of Iraq and the Levant (Isil), and their close friend Reeyad Khan appeared in one of the first Isil propaganda videos. Both Nasser and Aseel were added to the United Nations sanctions list in 2015. Nasser is believed to have been killed in an air strike in 2016.

Mr Muthana’s family say they tried to de-radicalise him in the run-up to his departure, even confiscating his passport, but he managed to obtain forged travel documents.

In 2015 his father Ahmed Muthana accused British authorities of not doing enough to stop his son from travelling to Syria.