The father of a British photojournalist held hostage by Isis (also known as Islamic State) militants has issued an emotional video appeal for his son to be released.

Paul Cantlie said he was proud of his son John, who was kidnapped in Syria in 2012 and recently appeared in three videos posted online by his captors.

"My family and I are trying to communicate with the Islamic State to deliver an important message regarding John and can only hope that it has been received as we have had no response," he said from a hospital bed after undergoing throat surgery.

"To those holding John: please know that he is a good man, he sought only to help the Syrian people and I ask you from all that is sacred, to help us and allow him to return home safely to those he loves and who love him."

Paul said he and the rest of his family "experienced great relief" seeing John in the videos posted online in September, in which the Briton is seen criticising Western action against the jihadists. It is believed the photojournalist recorded the lecture-format videos under duress.

"This was followed by the feeling of despair and helplessness," his father said. "John felt a strong need to help in the best way that he could: as an impartial and respected journalist he knew that he could make a difference by acting as a platform for the world to listen to and take notice, using his journalistic skills for the good of the people; as a friend and as a civilian.

"I have had many messages saying they cannot conceive what we, his family and all those who love him, must be feeling.

"Speaking entirely for myself, this is not how I had imagined I would be passing my 81st year," he added.

"I want John to know how very proud I am of him. I can think of no greater joy than seeing my dear son released and allowed to return home to us.

John's whereabouts are currently unknown but it is likely he is being held in Syria where other hostages James Foley, Steven Sotloff and David Haines were reportedly murdered in IS's de-facto capital of Raqqa.