The IDF had been in contact with Russia during the incident.

While Israel has no interest in getting involved in the Syrian civil war, he continued stressing nonetheless that “we are prepared for any developments.”

The IDF “will not tolerate violations of the 1974 Separation of Forces Agreement between Israel and Syria,” he said, referring to the UN Disengagement and Observer Force which monitors the Israeli-Syrian accord in the Golan Heights, adding that Israel holds the Syrian regime accountable for the actions carried out in its territory.

The UN’s Middle East envoy Nickolay Mladenov warned the UN Security Council following the downing of the jet that there has been “a disturbing trajectory of increasingly frequent and dangerous confrontations” between Israel and Syria. He called on all parties to abide by the 1974 agreement “and support the role of UNDOF in that regard.”

Prime Minister Benjamin Netanyahu said the downing was in response to a “gross violation of the 1974 separation agreements between Israel and Syria.”

“Our air defense systems identified a Syrian Air Force plane taking off from the Syrian air base T-4 and penetrating Israel. This is a gross violation of the 1974 separation agreements between Israel and Syria. I made it clear that we would not accept any such violation; we would not have any intrusion into our territory, either from the ground or from the air,” he said in a statement.

“Our forces acted accordingly. We insist that Syria strictly respect the separation agreements between us and them.”

Yoav Gallant (Kulanu), Israel’s Minister of Construction and Housing, said the downing sent a clear message to the region’s “axis of evil.”

“The downing of the Syrian plane is an important signal to the axis of evil – Iran, Syria and Hezbollah – that violating Israel’s sovereignty is crossing a redline,” Gallant said.

Syria has confirmed that the plane, which was taking part in an offensive against Islamic State group fighters in the Yarmouk basin, was downed by Israel but denied that it crossed into Israeli airspace.

“The Israeli enemy confirms its support for the armed terrorist groups and targets one of our warplanes, which was striking their groups in the area of Saida on the edge of the Yarmouk Valley in Syrian airspace,” a Syrian military official was quoted as saying by the state news agency SANA.

Sky News Arabic reported that the plane fell in the area of the Yarmuk Basin, a triangular border area between Syria, Israel and Jordan where there is intense fighting against the Islamic State group.

The last time Israel  shot down a Syrian jet by a Patriot missile was in 2014 shot down a Syrian jet with a Patriot missile was in 2014 after it penetrated 800 meters (2,600 feet) into Israeli air space. The crew managed to bail out of the plane, which landed in Syrian territory.

Incoming rocket-alert sirens blared throughout northern Israel around 1:30 p.m. in the Golan Regional Council, Jordan Valley and the city of Katzrin.

In recent weeks, Syrian government forces backed by Russian air power have been retaking large swathes of territory on the Syrian Golan Heights from rebel groups along the Israeli border. Iranian forces and affiliated Shi’ite militias are also said to be playing a minor role in the offensive.

“We have seen an increase in the intensity of the internal fighting in Syria, including aerial activity in recent weeks as part of the Syrian regime’s offensive to reoccupy the Syrian Golan Heights,” Manelis said.

It was the second-such incident of interceptors being fired in two days, opposite Syrian areas where Damascus’s forces have been routing rebels.

On Monday, Israel used its David’s Sling interceptor system for the first time, launching two missiles against two SS-21 Tochka tactical ballistic missiles launched from Syria. When the system determined that neither would hit Israeli territory, one of the interceptor missiles was ordered to self-destruct over Israel’s southern Golan Heights. The second David’s Sling interceptor missile fell inside Syria without intercepting the second SS-21.