Video of French hostage in Algeria authentic: Paris

New York (AFP) - A video showing a Frenchman kidnapped in Algeria by a group linked to Islamic State jihadists is authentic, French Foreign Minister Laurent Fabius said Monday in New York.

"The foreign affairs ministry confirmed, unfortunately, the authenticity of the video which carries the images of Herve Gourdel," Fabius told a press conference ahead of the UN General Assembly.

The militant group Jund al-Khilifa or "Soldiers of the Caliphate", which has pledged allegiance to the IS movement, said in the video that it had carried out Sunday's kidnapping.

It threatened to kill Gourdel within 24 hours unless France halts its air strikes against jihadist targets in Iraq.

The video shows the hostage squatting on the ground flanked by two hooded men clutching Kalashnikov assault rifles, as he asks French President Francois Hollande to intervene.

So far, France is the only country that has agreed to join the United States in air strikes against the extremist militants in northern Iraq.

In the video, the kidnappers say they are responding to a call from IS, posted just hours earlier, for Muslims to kill citizens of countries taking part in the US-led coalition against the jihadists who have seized of large swathes of Iraq and Syria.

"The threats made by this group are extremely grave and demonstrate the extreme cruelty of Daesh and all those associated with it," Fabius added, using the official French term for the IS group.