The ISIS version of events contradicts Egyptian security sources, who have said early investigations suggest the plane crashed due to a technical fault.
The Russian passenger plane crashed in Egypt's Sinai peninsula this morning after losing radar contact and plummeting from its cruising altitude, killing everyone aboard.
The Airbus A321, operated by Russian airline Kogalymavia under the brand name Metrojet, was flying from the Sinai Red Sea resort of Sharm el-Sheikh to St Petersburg in Russia when it went down in a desolate mountainous area of central Sinai soon after daybreak, the aviation ministry said.
A north Sinai security source said initial examination showed the crash was due to a technical fault, but gave no detail.
The plane, he said, had landed in a "vertical fashion", explaining the scale of devastation and burning.
The Russian Embassy in Cairo said it had been told by Egyptian officials the pilot had been trying to make an emergency landing at El-Arish.
"I now see a tragic scene," an Egyptian security officer at the site said. "A lot of dead on the ground and many who died whilst strapped to their seats.
"The plane split into two, a small part on the tail end that burned and a larger part that crashed into a rock. We have extracted at least 100 bodies and the rest are still inside."
Sinai is the scene of an insurgency by militants close to Islamic State, who have killed hundreds of Egyptian soldiers and police and have also attacked Western targets in recent months.
Russia, an ally of Syrian President Bashar al-Assad, launched air raids against opposition groups in Syria including Islamic State on September 30.
Security sources said there was no indication the Airbus had been shot down or blown up.