The Syrian government has reportedly withdrawn thousands of troops near the buffer zone between Israel and Syria in the Golan Heights, leaving a power vacuum that Israel is concerned could be filled with jihadist forces ready to turn their guns on the Jewish state.

Syria has redeployed divisions in the Golan to the area around Damascus to battle anti-government forces near the Syrian capital, according to a report in the British newspaper The Guardian on Sunday.

The redeployment near the Golan border was the most significant in 40 years, Western diplomats told The Guardian. Israel is concerned that the jihadist groups hostile to both Syrian President Bashar al-Assad and the Jewish state could move to fill the power vacuum in the Golan, creating a battlefront with Israel.

Four elite Syrian divisions made the Golan border Israel’s quietest for the past four decades, but tensions have simmered on the Golan Heights in the last few months. Last week, a mortar shell fired during fighting between Syrian rebels and loyalist troops landed in Israel. Errant explosives have landed several times in Israel-controlled Golan territory, and some cross-border incidents have prompted return fire from Israeli army patrols.

Israel is concerned that Assad’s weapons stockpiles, which include chemical weapons and advanced anti-aircraft missiles systems, could fall into the hands of either Shiite Hezbollah in Lebanon, which is loyal to Assad, has links to Iran, and is very hostile to Israel, or Sunni Islamist groups in Syria with links to international terrorist groups, which seek Assad’s ouster and are no friendlier to Israel.

On Sunday, an Israeli colonel told visiting Canadian Foreign Minister John Baird on a helicopter tour of the Golan that Israel is increasingly concerned about foreign, Sunni jihadists who have flocked to Syria to fight Assad, according to Canadian news outlet The Globe and Mail.