Abu Osama al-Masri, an Egyptian cleric and frontman of Sinai Province
Abu Osama al-Masri, an Egyptian cleric and frontman of the Sinai Province militant group Social media

Whitehall officials confirmed that Abu Osama al-Masri, an Egyptian cleric and frontman of Sinai Province – a militant group linked with Islamic State (IS) and active in the Sinai peninsula – is a person of interest in the 31 October crash of Russian flight KGL9268. Masri claimed responsibility for the Russian plane crash in an audio statement entitled entitled "We Downed It, So Die in Your Rage", issued on 4 November. This was the same day that David Cameron announced the suspension of British holiday flights to Sharm el Sheikh.

A Twitter account used by Sinai Province sent out a message on 4 November which seemed to suggest that a bomb, rather than a missile, was involved in the explosion.

Sinai Province's leader is a former clothes importer known by his alias Abu Osama al-Masri. The 42-year-old is a former scholar of the al-Azhar University in Cairo, a 1,000-year-old Sunni Muslim institution that gave an honorary doctorate to the Prince of Wales in 2008, according to a Sunday Times report.

In November 2014 his Sinai-based organisation pledged allegiance to Abu Bakr al-Baghdadi, the IS leader, in return for weapons, finance and bomb-making knowledge. The group are known to be very secretive. "Each cell doesn't know about other cells," an intelligence official told Reuters.

Another said: "It's a small number of militants, but it takes just one person to carry out a suicide bombing."

Prior to the explosion, US intelligence agencies also intercepted a message from the terrorists in Sinai that warned of "something big in the area".

It is understood that details about how the plane was brought down were also intercepted, but the officials have refused to give any further details. Security analysts described the latest developments as a "game changer" for IS.

"What we had seen so far were IS-inspired lone wolves, but this attack appears to be the result of close, consistent operational support," Mokhtar Awad of the Centre for American Progress said.

Intelligence officials believe that a member of the Sinai Province group smuggled a bomb into the luggage hold of the Metrojet plane at Sharm el Sheikh airport. A CCTV station where security officials were expected to constantly monitor baggage handlers was often abandoned. It was "50-50" a staff member told The Independent on Sunday, adding that "it happens sometimes that no one is there".

There are unconfirmed reports that British jihadis trained in Syria with an "electronics background" could have assisted in making the bomb which caused the fatal plane crash. British intelligence picked up "chatter" which reportedly featured jihadists with Birmingham and London accents celebrating in Egypt after the aircraft came down.

Investigators are concluding that the noise heard in the final seconds before the Metrojet flight 7K9268 downed in Sinai Peninsula was caused by an explosive device. One intelligence official told CNN: "It's 99.9% certain. We believe it was likely brought down by a bomb."