Isis’s militant branch in the Sinai Peninsula has released an audio message claiming it brought down the crashed Russian Metrojet plane - and challenging Egyptian authorities to “prove we did not”.

Wilayat Sinai (Sinai Province) said it would reveal its modus operandi in due course, in a recording entitled: “We downed it, so die in your rage”.

Some experts have questioned the militant group's claim of responsibility, pointing out it has failed to provide any proof. The Amaq news website, which publishes information from Isis sources, reported Isis’s original claim within hours of the plane coming down.

Officials have poured scorn on suggestions the crash was an attack carried out by Isis, with the Egyptian President Abdel Fattah al-Sisi describing such claims as “propaganda”.

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Wednesday’s audio message was believed to carry the voice of Wilayat Sinai’s Abu Osama al-Masri, who has made recordings for the group in the past.