Israel has destroyed a Syrian armoured vehicle in retaliation after a mortar shell landed on its territory in the first direct confrontation between the countries since the Syrian uprising broke out.
The response by Israel, the second in two days, increased fears that it could be drawn into the civil war next door.
Israel has steadfastly tried to avoid getting sucked into the Syrian conflict, but it has grown increasingly worried after a series of stray mortar shells have struck territory in the Israeli-controlled Golan Heights. Israeli military believe the mortar fire is spilling over from intense fighting near the frontier between Syrian president Bashar Assad's army and rebel forces trying to oust him, and not an overt attempt to hit the Jewish state.
But Israel is starting to question that assessment. "We thought it was spillover, but today we're not sure," said one senior military official.
Syria's civil war also shook the country's northern neighbour, Turkey, after a Syrian jet bombed a rebel-held area near the frontier, killing at least six people.
Israeli officials have long feared that the embattled Assad might try to draw Israel into the fighting in an act of desperation.
In a statement, the military said Israeli tanks targeted the "source of fire" in Syria after the mortar shell landed in an open area of the Golan Heights. It confirmed "direct hits" on the targets.
Israeli military officials said an armoured vehicle carrying "Syrian mobile artillery" was hit.
Mortar shells have landed in the Golan over the past week, and early this month Syrian tanks accidentally crossed into a buffer zone along the frontier of the Golan for the first time in nearly 40 years. Israel captured the Golan, a strategic plateau, from Syria in the 1967 Mideast war and subsequently annexed it.
After weeks of standing still, Israel responded for the first time on Sunday, firing what it called a "warning shot" into Syria after another mortar shell strayed across the frontier and landed near an Israeli military post. Israel also warned of a tougher response if the attacks persisted.