Cairo, Moscow: Daesh on Wednesday insisted it brought down a Russian plane that crashed in Egypt’s Sinai Peninsula, providing no new details but challenging sceptics to prove otherwise.

The militant group had claimed on Saturday that it downed the Airbus in Sinai, where its Egypt affiliate is based, but provided no details, prompting scepticism about its involvement.

“We are under no obligation to explain how it came down,” Daesh said in the statement, posted a day after it released a video showing its fighters in Iraq celebrating the incident.

“Bring the wreckage and search it, bring your black boxes and analyse them, and tell us the results of your investigation,” a man said in the recording.

“Prove that we didn’t bring it down, and how it came down. We will detail how it came down at the time of our choosing.”

Investigators continued on Wednesday analysing data from the black boxes of the plane, a charter flight operated by Russian airline Kogalymavia, which went down 23 minutes after take off from Sharm Al Shaikh.

Authorities have warned that the probe could last several weeks or months, depending on the conditions of the recordings in the black boxes.

US Director of National Intelligence James Clapper also said this week it was “unlikely” Daesh was involved, but he did not rule out the possibility.

The airline itself has ruled out technical fault or human error, drawing fire from the head of Russia’s aviation authority. Alexander Neradko said the airline’s conclusions were “premature and not based on any real facts”.

Experts say the fact that debris and bodies were strewn over a wide area points to a mid-air disintegration of the aircraft.

That leaves two possibilities - a technical fault that caused the plane to disintegrate or an explosion caused by a bomb smuggled on board, according to experts.

US officials told CNN and other US television networks that a military satellite had detected a heat flash at the time of the crash, which could point to a catastrophic event during flight, possibly a bomb explosion.

Search operations had been extended to a radius of about 40 km.

President Vladimir Putin has described the crash — Russia’s worst-ever air disaster — as a “huge tragedy”.

Relatives of the victims have begun the process of identifying the bodies after two planes delivered the remains of many to Saint Petersburg.

Saint Petersburg deputy governor Igor Albin told reporters that 33 crash victims had already been identified.

Family members provided DNA samples at a crisis centre set up near Saint Petersburg’s Pulkovo airport, now the site of an impromptu memorial where people have brought flowers and toys to commemorate the victims, many of them children.

IS has deployed shoulder-fired anti-aircraft missiles in the past but they are not known to possess weapons that could bring down an airliner flying at high altitude.

The militants have killed hundreds of policemen and soldiers since the military overthrew Islamist president Mohamed Morsi in 2013.

They say their attacks have been in retaliation for an ensuing police crackdown in which hundreds of Morsi supporters have been killed and thousands, including the ousted president, jailed.

In an interview with the BBC ahead of his trip to Britain, Sisi insisted the Sinai “is under our full control”.