Russia Sinai plane crash
An Isis affiliate continues to claim responsibility for the downing of the A321 Russian airliner lie over SinaiAFP

The Egyptian branch of Islamic State (Isis) has released an audio statement reiterating its claim to have brought down the Russian jet that crashed on 31 October, challenging Egyptian authorities to prove they did not do it.

In the audio, Sinai Province spokesman Abu Osama al-Masri claimed the Kogalymavia Airlines flight was brought down a year after the group, then named Ansar Beit al-Maqdis, pledged its allegiance to IS leader Abu Bakr al-Baghdadi.

"We are the ones who brought it down," he claimed in the statement, adding that the method will be revealed "in the time of our choosing".

Flight 7K9268 from the Red Sea resort of Sharm el-Sheikh to St Petersburg crashed in the Hassana area of the restive Sinai peninsula, killing all 224 people on board, mostly Russian tourists.

Security experts, as well as Russian and Egyptian officials, have cast doubt over IS's claims of responsibility. It seems unlikely that with the weapons systems at their disposal the Sinai Province militants would be able to down a commercial jet cruising at more than 30,000 feet. Russian transport minister Maxim Sokolov called their claims a "fabrication".

US satellite imaging would also appear to rule out a surface-to-air explosion. The intelligence has shown just one heat signature at the time of the crash, indicating an explosion or fire inside the plane caused it to break up in the air.

Several airlines, including Emirates, Lufthansa and Air France-KLM, have nevertheless said they will not fly over the area until reasons for the crash are clear.

The jet was cruising at about 31,000 feet, when, in one minute, it lost 5,000 feet and of 300 kph (186 mph) in speed, according to Metrojet's deputy general director Alexander Smirnov. The crew "totally lost control" and was not able to radio aviation authorities.