A 55-year-old French mountain guide today became the first victim of the threatened “revenge” executions following western air attacks on Isis forces in Syria and Iraq. A video placed online by an Algerian jihadist group linked to Isis appeared to show the beheading of Hervé Gourdel, who was kidnapped earlier this week in a mountainous region of Algeria. French officials said they believed the video to be authentic but could not immediately confirm Mr Gourdel’s death. Isis called for revenge killings of westerners – especially American and French citizens – after France joined the US and Arab states in air raids on jihadist forces. It was later revealed that Mr Gourdel had been seized by the Jund al-Khilafah, or Soldiers of the Caliphate, jihadist group while trekking in the Tizi Ouzou massif 110 kilometres east of Algiers. Mr Gourdel was a professional guide in the Mercantour Alps in the south of France and lived in Nice. His twin passions were mountaineering and photography. In the video placed online today, he is seen kneeling in a grey top emblazoned with a blue triangle in the shape of a mountain. Behind him are four masked men.