A video has been released showing a British man believed to be held captive by Islamic State (IS) militants.

In the video, the man says he plans to reveal in a series of what he called programs the "truth" about the jihadist group that controls swaths of Iraq and Syria.

The man, who AFP identified as freelance photojournalist John Cantlie, says he and others have been abandoned by the United States and Britain governments, and asks why they are so keen to get involved in another war.

There was apparently no immediate threat to his life and no IS militants are seen in the video.

Cantlie was taken hostage after travelling to Syria in November 2012.

The IS militants have killed three western hostages -- a Briton and two Americans -- and has threatened the life of another British man.

Based on reporting by AFP and the BBC