The claims (released on the Internet) that the ISIL caused the accident are a way to undermine Egypt's stability, security and image, the Egyptian president told journalists.
"Believe me, the situation in the Sinai, particularly in the area of the air crash, is under full control of Egyptian authorities."
Meanwhile, US Intelligence Chief, James Clapper, said to lack evidence about a likely terrorist action behind the accident that caused the death of 217 passengers and seven crew members.
Experts from Egypt, Russia and Ireland and from the plane-making firm, Airbus, started to decode the plane's black boxes on Tuesday.
Meanwhile, executives of the Russian Kogalymavia airline said the plane was in perfect technical conditions, so "the only explanation points to external causes."
However, a preliminary analysis of the wreckage has not yielded any information underpinning the Kogalymavia authorities' claims.
For the time being, the investigators have not ruled out any hypothesis as why the plane disintegrated in mid-air.
Possible explanations include a sudden mass depressurization or decompression or structural flaws.
The flight of the Kogalymavia plane took off from Egypt's resort in Sharm El Sheikh, in the Sinai Peninsula, bound for Saint Petersburg, Russia.
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