Violence from the Syrian civil war is likely to spill over into Israel again, and IDF troops along the northern border have been placed on high alert, Chief of Staff Lt.-Gen. Benny Gantz said on Sunday.

Together with IDF Spokesman Brig.-Gen. Yoav Mordechai and other top brass, Gantz toured the Israeli-Syrian border on Sunday and observed both regime soldiers and rebel forces operating in Syria.

During his visit, explosions and other sounds of fighting just across the border in Syria were readily audible.

The IDF chief’s comments came a day after three Syrian tanks briefly crossed into the demilitarized zone in the Golan Heights, the first such incident in 40 years. In response, Israel raised its alert level and lodged a protest with the UN peacekeeping forces stationed in the DMZ.

Gantz instructed troops in the Golan Heights to stay on alert in case of further spillover from the fighting. “It is a Syrian issue, but it can become ours,” he told a group of Golani Brigade officers.

In late September, a rocket fired from Syria landed in the central Golan Heights. A day earlier, several mortar shells from Syria fell in agricultural land in the northern Heights, in the first reported instance of munitions spilloverinto Israel from the Syrian civil war.

In July, Jerusalem filed a protest with the UN over the incursion of Syrian soldiers into the DMZ during fighting with rebel forces.

AP contributed to this report.