Israel downed a drone over the occupied Golan Heights on Sunday, the army said, amid mounting tension on the UN-patrolled armistice line with Syria on the strategic plateau.
Air defences "successfully intercepted an unmanned aerial vehicle (UAV) that breached Israel airspace above the border with Syria," an army statement said.
"We have said several times that we shall respond to any violation of our sovereignty," it added.
Defence Minister Moshe Yaalon meanwhile toured the region, as the army sent reinforcements along the armistice line and deployed armoured troop carriers, an AFP photographer said.
Yaalon warned that Israeli "tolerance" should not be tested.
"These past weeks we have proven that our tolerance is minimal when our integrity is struck, either intentionally or unintentionally," he said.
Heavy fighting between Syrian government troops and opposition forces overflowed into the buffer zone separating Syrian and Israeli-occupied territory at the weekend.
Dozens of Filipino UN peacekeepers escaped the hot zone overnight after rebels rammed their Golan Heights outpost with armed trucks, the Philippine military said.
A UN statement said the United Nations Disengagement Observer Force (UNDOF) "confirms that the Filipino forces formerly surrounded by armed elements... have relocated to an alternate site and are safe."
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But UNDOF troops "remain on high alert" as the fate of 44 Fijian peacekeepers abducted on the Golan by Syrian rebels remains unknown, it said.
The statement said the peacekeepers "continue to be detained by armed elements.
"At this time, no additional information on their status or location has been established. The United Nations continues to actively seek their immediate and unconditional release."
Israel closed off the area around the Quneitra crossing on the Golan on Wednesday after an officer was wounded by stray fire as Syrian rebels seized control of the site.
On August 24, rocket fire from Syria hit several points in the Israeli-controlled zone but there were no casualties.
In June, Israeli warplanes attacked Syrian military headquarters and positions after an Israeli teenager was killed in what the Jewish state said was a cross-border attack by forces loyal to Syrian President Bashar al-Assad.
Some incidents have been put down to stray fire from fighting between Syrian government troops and rebel forces.
Israel seized 1,200 square kilometres (460 square miles) of the Golan Heights during the Six-Day War of 1967, then annexed it in 1981 in a move never recognised by the international community.
UNDOF has been monitoring a ceasefire since 1974.