A fighter of the Islamic State (ISIS)
A fighter of the Islamic State (ISIS)Reuters

The family of British hostage Alan Henning made a dramatic appeal for his release on Saturday night, the Telegraph reported.

The appeal follows rumors on social networking sites that the 47-year-old taxi driver from Manchester had become the latest hostage to be killed by Islamic State (IS).

His wife Barbara Henning said, "Alan is a peaceful, selfless man who left his family and his job as a taxi driver in the UK to drive in a convoy all the way to Syria with his Muslim colleagues and friends to help those most in need.”

"When he was taken he was driving an ambulance full of food and water to be handed out to anyone in need. His purpose for being there was no more and no less. This was an act of sheer compassion,” she added.

"I cannot see how it could assist any State's cause to allow the world to see a man like Alan dying.”

"I pray that the people holding Alan respond to my messages and contact me before it is too late. I implore the people of the Islamic State to see it in their hearts to release my husband," she said, adding her pleas to IS had not been responded to.

Henning was kidnapped just half an hour after entering Syria last year.

He was driving an ambulance on behalf of Rochdale Aid 4 Syria, which raised money on behalf of Al-Fatiha Global, a registered charity currently under investigation by the Charity Commission after one of its leaders was photographed with his arms around two hooded fighters carrying machine guns.

After his capture, Henning told other hostages “don’t worry about me”, believing he would be freed “in no time because I’m just an aid worker”.

His whereabouts were only revealed last week when he was shown kneeling in the sand, wearing an orange jumpsuit, in a video produced by IS jihadists which also showed the murder of David Haines, another British aid worker.

The Foreign Office said they had no further update on Henning.

Islamic State has released two previous videos showing the execution of the American journalists James Foley and Steven Sotloff. The group threatened to kill Haines at the end of the Sotloff video.

On Friday, IS came out with a 55-minute feature length film entitled "Flames of War: Fighting Has Just Begun."

The film, shot in a documentary-style, warns of an imminent direct conflict against America, and is narrated by a man with an accent suggesting American or Canadian roots.

"A proxy war won't help you in Sham (Syria) just as it didn't help you in Iraq," the video concludes. "As for the near future, you will be forced into a direct confrontation."

The message refers to U.S. President Barack Obama's insistence that he will not send U.S. ground forces back into Iraq or into Syria to confront the rising ISIS threat, instead arming Syrian rebels to fight IS "by proxy" and conducting airstrikes.