JERUSALEM (JTA) — Israel offered its condolences to Russia over the crash of a Russian passenger plane in Sinai which killed all 224 people aboard.

“I offer condolences to the government of Russia, to President Putin, to the Russian people and, of course, to the families of the victims,” Israeli Prime Minister Benjamin Netanyahu said Sunday. “This was a very serious disaster. We share in their grief. We are, of course, in continuous contact with the governments of Russia and of Egypt regarding the circumstances of the incident.”

The Sinai affiliate of the Islamic State claimed responsibility for bringing down the aircraft on Saturday, saying it was in retaliation for Russian airstrikes on rebels in Syria’s civil war. Russia’s transportation ministry rejected the claim, pointing out that the group did not offer any evidence as to how it was able to cause the plane to crash.

Egyptian Prime Minister Sharif Ismail said experts do not believe that weapons held by the Islamic State could down a plane at the altitude of the flight when it came down, the BBC reported.

Russian officials opened an investigation into the crash, looking for gross negligence and safety violations.

Israel Defense Forces Spokesman Peter Lerner tweeted Saturday that the IDF assisted with aerial surveillance in efforts to locate Metrojet Flight 7K9268, traveling from the Egyptian resort town of Sharm el-Sheikh to St. Petersburg in Russia.

He later tweeted:  “The IDF has offered continued assistance to both #Russia and #Egypt if required. #7K9628”

Most of the passengers on the plane were Russian tourists, including Anna Tishinskaya, 27, a former program director for Hillel Russia.

Three airlines – Emirates, Air France and Lufthansa – have decided not to fly over the Sinai Peninsula until a determination is made as to how the plane crashed, the BBC reported.

Russia is observing a day of mourning on Sunday.