Swedish prosecutors say Osama Krayem took part in the murder of the pilot, Muath Al-Kasasbeh, who was burned alive in a cage by Islamic State militants after his plane went down in IS-occupied territory in late 2014.

Daniel O'Toole, an agent from the US's Federal Bureau of Investigation, was questioned about his interrogation of a British member of Islamic State to understand what role Krayem played in the murder of the pilot, which was filmed for a widely diffused video.

Alexanda Kotey, who has since been stripped of his British citizenship, was arrested by Kurdish forces in the east of Syria and extradited in 2020 to the US, where he agreed to provide information about IS, and specifically its elite Liwa Al Sadiqeen unit.

"According to Alexanda Kotey, was Osama Krayem a member of Liwa Al Sadiqeen?" the prosecutor asked the FBI agent, who responded "yes".

Krayem has testified that he was only on the scene of the pilot's murder for 15 to 20 minutes without knowing what was about to happen.

"Is it possible that a person who was not approved in advance to take part in this production, be hired as an extra in the video?" the prosecutor asked the FBI agent, who said "no".

Krayem's lawyer has contested the veracity of Kotey's claims.

"Is it really possible to verify everything that he said, all 900 pages?" he asked, to which O'Toole responded that it was not possible.

The trial is to run until 26 June.