A VIDEO apparently showing the beheading of British hostage Alan Henning, who was kidnapped by IS militants, has been released on the internet.

The footage appears to show the 47-year-old aid worker, who was kidnapped last December in Syria by IS militants, kneeling beside a militant dressed in black in a desert setting.

Mr Henning, a former taxi driver from Salford, was last seen at the end of a video released last month following the beheading of fellow British captive David Haines.

The news, which broke shortly before 9.30pm tonight, follows a visit to the region by British Prime Minister David Cameron.

On hearing of the murder, Mr Cameron tweeted: "The brutal murder of Alan Henning by ISIL shows just how barbaric these terrorists are. My thoughts are with his wife and their children."

The same hooded man believed responsible for the deaths of two US journalists and Mr Haines appears in the video.

Threats are then made to kill another US hostage, named as former soldier Peter Kassig, at the end of the footage. 

Mr Cameron announced the deployment of two more RAF Tornado fighter bombers to join the attacks on Islamic State (IS) militants as he made a surprise visit to the base where they are operating.

The Prime Minister, arriving at RAF Akrotiri in Cyprus, also promised that the operational life of the aircraft - which was due to be withdrawn from service next year - would be extended until 2016.

The two additional Tornado GR4s will lift the number deployed to eight, enabling them to sustain the tempo of sorties at around two a day.

The RAF has now carried out a series of strikes on IS forces since Parliament authorised British involvement in the international military campaign last week.

The latest saw Brimstone missiles and Paveway bombs deployed in support of Kurdish troops advancing on extremists in the north west of the country.

Earlier this week Mr Henning's wife Barbara pleaded for him to be freed.

She said: "I ask Islamic State please release him, we need him back home."

She added: "Some say wrong time, wrong place. Alan was volunteering with his Muslim friends to help the people of Syria. He was in the right place doing the right thing."

Mrs Henning revealed she had received an audio message of her husband pleading for his life, and had been told that a Sharia court had found him innocent of being a spy.

She told BBC News: "We are at a loss why those leading Islamic State cannot open their hearts and minds to the truth about Alan's humanitarian motives for going to Syria and why they continue to ignore the verdicts of their own justice system.

''Surely those who wish to be seen as a state will act in a statesmanlike way by showing mercy and providing clemency. I ask again, supported by the voices across the world, for Islamic State to spare Alan's life."

The video shows Mr Henning saying: "I am Alan Henning. Because of our Parliament's decision to attack the Islamic State, I, as a member of the British public, will now pay the price for that decision."

The man dressed in black, who speaks with a British accent, then makes a direct statement to Mr Cameron: "The blood of David Haines was on your hands Cameron. Alan Henning will also be slaughtered, but his blood is on the hands of the British Parliament."

After the killing the video focuses on Mr Kassig.

The militant adding: "Obama, you have started your aerial bombardment in Sham [Syria], which keeps on striking our people. So it is only right that we continue to strike the necks of your people."

The Foreign Office said: "We are aware of the video and are working urgently to verify the contents. If true, this is a further disgusting murder.

"We are offering the family every support possible; they ask to be left alone at this time."

MPs were swift to condemn the apparent murder, one describing it as "an attack on humanity".

Liberal Democrat party president Tim Farron said: "Alan Henning should be remembered for what he was - a kind hearted, selfless man who wanted to help others. My prayers are with his family."

Shadow cabinet minister Jonathan Ashworth said the video emerged only hours after a vigil for his safe return by people "of all faiths and none" in Leicester.

"Dreadful devastating news," he said.

Labour's Pat McFadden said it was the "senseless killing of an innocent man. An attack on humanity."