Israel warned Syrian President Bashar al-Assad on Friday to prevent his anti-insurgency sweeps from spilling over into the Israeli-occupied Golan Heights, saying it was prepared to defend itself.

The Golan, lost by Damascus in the 1967 Middle East war and mostly quiet for decades, was repeatedly hit by what the Israelis described as stray Syrian ordnance this week.

No one was hurt but nerves were jangled in Israel, which has tried to keep out of the conflict ravaging its old enemy next door.

"We see the regime in Syria as responsible for what is happening along the border," Israeli Vice Prime Minister Moshe Yaalon said in a statement.

Referring to the 19-month-old Syrian civil war, he said: "If we see that it is spreading in our direction, we will know how to defend the citizens of the State of Israel and the State of Israel's sovereignty."

Yaalon said Syria had previously "conducted itself appropriately" after receiving such messages. "I hope that in this case, too, there will be someone in Syria who takes matters in hand."

Israel annexed the Golan in 1981 in a move not recognised internationally. In all past peace talks with Israel, Syria has insisted on the strategic plateau's return. The two countries signed a disengagement agreement in 1974, a year after another Arab-Israeli conflict, but are still technically at war.

Asked about a mortar bomb that landed in a Golan settlement on Thursday, Israeli Defence Minister Ehud Barak linked the incident to Syrian military operation against rebels nearby.

"We have made clear via UNDOF that we intend for there not to be shells falling on us," Barak told Israeli television, referring to a United Nations observer group on the Golan.

Barak did not elaborate on Israel's plans, saying only: "I hope this will not continue, and that the rebels will win in Syria, that Assad will fall and that, at long last, a new stage in the life of Syria will begin."