Terror group ISIL has released a video of a British freelance photojournalist, John Cantlie, in which he says he is being held captive.

In the video posted on YouTube, Mr Cantlie, wearing an orange jumpsuit, speaks to the camera in the style of a news report and promises to reveal in an upcoming series of programs the "truth" about the jihadist group that has seized parts of Iraq and Syria.

Speaking in English with Arabic subtitles, Cantlie says in the 3:21-minute video - titled "Lend Me Your Ears" - that he plans to reveal "the truth behind the systems and motivation of the Islamic State".

Unlike the majority of the extremists group’s media output, the video contains no threats – only a promise to show another side to the story.

The video follows earlier ISIL releases that depicted the brutal beheadings of two US journalists, James Foley and Steven Sotloff, and that of British aid worker David Haines.

"I know what you're thinking": Mr Cantlie reads from a script in the video. (YouTube)

Mr Cantlie, like those executed in previous clips, reads what appears to be a scripted statement, denouncing Western government policy and media outlets.

"Now, I know what you're thinking," he says.

"You're thinking, 'He's only doing this because he's a prisoner. He's got a gun to his head and he's being forced to do this.'

"Well, it's true - I am a prisoner. That I cannot deny.

"But seeing as how I've been abandoned by my government and my fate now lies at the hands of the Islamic State, I have nothing to lose.

"Maybe I will live and maybe I will die."

Mr Cantlie promises to reveal the "truth" about ISIL in a series of videos. (YouTube)

The video features the same high production values that defined earlier ISIL propaganda clips, with title graphics, Arabic subtitles and multiple cameras apparent.

The broadcast-style theme is continued as the reporter signs off in newscaster fashion.

“Join me for the next program and I think you might be surprised at what you learn,” he says.

Mr Cantlie, who had contributed to British newspapers including The Sunday Times and Sunday Telegraph, as well as to Agence France-Presse, said he was captured after travelling to Syria in November 2012.

He had previously been detained along with a Dutch photographer by extremists in Syria in July 2012 but was reportedly released after nine days.

It was not clear when the video was shot, but in it Mr Cantlie referred to recent events including IS taking control of large parts of Iraq in June.