Israel believes the Russian passenger plane that crashed in the neighbouring Egyptian Sinai on Oct. 31 was brought down by militants who probably used a bomb, Defence Minister Moshe Yaalon said on Monday.
Israel, which closely monitors the Sinai, had previously declined to comment publicly on the cause of the disaster, even as the United States and Britain said they had intelligence assessments that the plane was bombed by Islamist insurgents.
"There is a high probability, from what we understand, that this was a terrorist attack - the highest of probabilities," Yaalon told Israeli reporters, according to his spokesman.
"We are not taking part in the investigation, but from what we hear and understand, I will be surprised if it turns out that this was not a terrorist attack whereby a bomb exploded inside the aircraft," the spokesman further quoted Yaalon as saying.
Yaalon did not elaborate. Nor did he confirm or deny a CNN report that Israel's spy services had provided communications intercepts gathered in the Sinai to U.S. and British analysts.
Egypt and Russia have yet to formally announce the cause of the crash. Both countries were upset by the Western bomb assessments published last week, which spurred a wave of foreign flight cancellations to Sinai's Red Sea resorts.
Israel deems Egypt a key security partner and has lobbied for U.S. support of Cairo's counter-insurgency efforts in Sinai.
On Friday, Yaalon's senior adviser on Middle East affairs, Amos Gilad, voiced concern that premature international speculation about the cause of the Russian airliner disaster would hurt Egypt's lifeblood tourism sector.
"I would prefer that first there be an investigation and then a unified announcement be made," Gilad told Israel's Channel One television.
"The Egyptians are tackling the dangerous terrorism called ISIS (Islamic State) in Sinai," he said. "The world should support them."
Israel's best-selling Yedioth Ahronoth daily reported on Friday that Israeli radar had spotted the Russian plane plummeting "like a rock" but no sign of a missile launch beforehand, lending weight to the theory it had been bombed.
Israeli forces were on high alert for a possible Islamic State attempt to hijack a plane in Egypt and crash it into a city in Israel, Yedioth said.
The newspaper added that warplanes had been scrambled repeatedly in response to suspicious aircraft activities in Sinai. Israeli officials declined comment.