An Isis-inspired group calling itself Jund al-Khilafah in the Land of Kinana (Egypt) has vowed to fight for the Islamic State (also known as Isis) and threatened to slaughter Christians in Egypt.

The group, which draws its name from Algeria's Jund al-Khilafah (Soldiers of the Caliphate), promised to strike American interests and the "worshippers of the Cross" in Egypt, according to SITE monitoring group.

Jihadist militants have been operating in Egypt's restive Sinai Peninsula since the 2011 revolution against Hosni Mubarak. A group called Ansar Bayt al-Maqdis (Champions of Jerusalem), carried out attacks against the Egyptian army and Israel.

In the latest video, the Islamists showed the beheading of four men accused of working for Mossad, Israel's intelligence agency. Inspired by al-Qaida, Ansar Bayt al-Maqdis is not known to be affiliated to the Islamic State.

Conversely, Algeria's Isis-linked group recently killed French hostage Hervé Gourdel in a gruesome beheading video that emerged online.

The Islamist fighters also pledge allegiance to Isis leader Abu Bakr al-Baghdadi saying: "Here are your soldiers fighting those you fight and making peace with those you make peace with."