JERUSALEM (Reuters) -- Israel fired a guided missile into Syria on Sunday in a potent "warning shot" after mortar fire from fighting between Syrian troops and rebels hit the Israeli-occupied Golan Heights for the second time in four days.
Israel Radio said it was the first direct engagement of the Syrian military on the Golan since the countries' 1973 war. It highlighted international fears that Syria's civil war could ignite wider regional conflict.
An Israeli military source said troops fired a Tammuz missile towards a Syrian army mortar crew that had launched a shell which overshot the Golan disengagement fence on Sunday, exploding near an Israeli settlement without causing casualties.
The missile, known internationally as Spike, can be guided to its target by an operator who sees a live video image from an on-board camera in its nose. There were no reported casualties in what was evidently a demonstration of fire-power.
In an official statement, the Israeli military said soldiers had "fired warning shots towards Syrian areas" but did not mention the missile or its target destination.
"The IDF has filed a complaint through the UN forces operating in the area, stating that fire emanating from Syria into Israel will not be tolerated and shall be responded to with severity," it said.
Earlier Israeli Defense Minister Ehud Barak threatened to respond should stray Syrian ordnance continue to strike the Israeli-occupied Golan.
"The message has certainly been relayed. To tell you confidently that no shell will fall? I cannot. If a shell falls, we will respond," Barak told Israel's Army Radio, without elaborating.
A Syrian mortar bomb, one of a salvo, hit an Israeli settlement on the Golan on Thursday but did not explode. Earlier this month, Israel complained to the United Nations after three Syrian tanks entered a Golan demilitarized zone. Israel also said a stray Syrian bullet hit one its army jeeps on patrol.
Israel has tried to stay out of the 19-month-old Syrian insurgency, reluctant to be drawn into another war and unclear about whether a post-Assad Syria might prove more hostile.
But Barak said on Thursday he hoped the rebels would win, Assad would fall and that "a new stage in the life of Syria will begin".
Israel's military chief, Lt-Gen. Benny Gantz, warned troops on the Golan Heights a week ago: "This is a Syrian issue that could become our issue."