IDF soldiers on Sunday morning fired a Tammuz missile at a Syrian army position in Tel Fares, from which shots were fired both that day and the previous day across the border into the Israeli-controlled Golan Heights. The missile destroyed the Syrian post and reportedly wounded two gunmen there.

A military spokesman said the soldiers responded with “accurate fire toward the Syrian post from which they were fired upon.” He could not say whether regular Syrian forces or rebels fired. He spoke on condition of anonymity because he was not authorized to speak to the media.

Later reports suggested the gunfire at Israel had come from Syrian army forces, but that it was not clear whether it had been deliberately aimed at Israel.

On Saturday, an IDF patrol convoy in the Golan Heights came under rifle fire from the same Syrian army post as fighting continued along Israel’s borders with Israel and Jordan. No one was hurt, but the rounds caused damage to several IDF patrol vehicles.

It was unclear, in that incident too, whether the rifle fire was deliberately aimed at the IDF vehicles.

Defense Minister Moshe Ya’alon said Israeli was implementing a no-tolerance policy in response to any Syrian fire.

“We deplore the shooting attack on IDF forces inside Israeli territory,” Ya’alon said in a statement. “In response, the IDF retaliated according to the policy instated by the government: Any breach of Israeli sovereignty from the Syrian side will immediately precipitate the suppression of the sources of fire.”

The defense minister added that Israel held the Syrian government responsible.

“We were forced to act in a targeted way and to attack and destroy the post from which this (gunfire) took place,” IDF Chief of General Staff Lt. Gen. Benny Gantz said Sunday. “We will continue to operate in the Golan Heights with reason and caution, but where determination and assertive and offensive action is needed, that will also take place.”

The rebel effort to overrun the Quneitra region along the ceasefire line separating Syria and Israel has heightened worries that Islamic extremists among those fighting Assad could take over the frontline with Israeli troops and gain a potential staging ground for attacks on the Jewish state.

The frontier has largely been calm in the nearly four decades since the two countries fought a war over the Golan Heights that ended with a UN-monitored ceasefire. But Israeli military officials have expressed concern that a rebel takeover could upset the calm maintained by Assad and his predecessor and father, the late Hafez Assad.

Those fears have been compounded by increasing influence wielded by extremist groups over the divided rebels and the increasing international isolation of the regime.

“We are seeing terror organizations gaining footholds increasingly in the territory,” said Lt. Gen. Benny Gantz, Israel’s military chief at a conference in Israel last week. “For now, they are fighting Assad. Guess what? We’re next in line.”

Israel says it is trying to stay out of Syria’s civil war, but it retaliated for sporadic Syrian fire that spilled into Israeli communities on the Golan Heights on several occasions over the past few months.

An Israeli military official this week said the entire border area has become a “playground” for skirmishes between rebels and the Syrian army.

The United Nations Disengagement Observer Force, known as UNDOF, was established to monitor the ceasefire in May 1974 by a UN Security Council resolution.

Last month, members of the Yarmouk Martyrs Brigade held 21 Filipino UNDOF peacekeepers hostage for four days, raising concerns about the future of UN operations in the area.