The Israeli Air Force shot down a Syrian fighter jet that traveled two kilometers into Israeli airspace on Tuesday afternoon, the military said. Syrian state-run media confirmed the jet was shot down but said it was inside its own airspace.

“Two Patriot missiles were fired at a Syrian Sukhoi-model fighter jet,” the Israel Defense Forces said in a statement.

The IDF said the aircraft was monitored as it approached the border with the Golan Heights.

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“It penetrated two kilometers into Israeli airspace and was shot down,” the army said.

According to Sky News Arabia, the plane crashed inside southwest Syria, in the Yarmouk Basin, an area still under the control of the Islamic State terrorist group.

One of the pilots, identified as Col. Amran Mara’e, was killed when the plane was shot down, a Syrian military source told Sputnik, a Russian government-backed news outlet. The fate of the other airman was not immediately known.

The official Syrian news outlet SANA claimed the plane was inside Syrian airspace at the time it was targeted.

According to SANA, Israel fired at “one of our war planes, which are leveling [terrorist] encampments in the Saida region on the outskirts of the Yarmouk Basin, in Syrian airspace.”

A military source quoted by SANA accused Israel of aiding “terrorists” in the country’s southwest, where the Syrian air force has been conducting extensive bombing raids throughout the day against a number of opposition groups.

This was the first time that Israel shot down a Syrian fighter jet since 2014, when another Russian-made Sukhoi fighter jet entered Israeli airspace and was targeted with a Patriot missile.

The Israeli military said it was not immediately certain if the plane was a Sukhoi-22 or a Sukhoi-24, two different types of Russian-made fighter jets in use by the Syrian Air Force.

According to the Al-Masdar news outlet, which is generally seen as supportive of the Assad regime, the felled aircraft was a Sukhoi-22 fighter jet.

The IDF said it had noticed increased air force activity in southwestern Syria, near the border, since the morning.

“We have issued numerous warnings through numerous channels and in various languages to make sure that no one on the other side violates Israeli airspace or threatens Israeli civilians or sovereignty,” IDF spokesperson Lt. Col. Jonathan Conricus told reporters.

The spokesman said Israel has been in regular contact with the Russian military, which operates extensively in southwestern Syria, in order to prevent any conflict with Moscow.

According to the IDF, the fighter jet took off from the Iran-linked T-4 air force base in central Syria, which Israel has bombed in the past, and traveled “at high speed” toward the Golan Heights.

Conricus said there was no “confusion” about the fact that this was a Syrian fighter jet. In the past, Israel has hesitated in shooting down incoming aircraft out of concerns they might belong to Russia.

Israel stressed that it will continue to enforce the 1974 Separation of Forces Agreement, which requires Syria to abide by a demilitarized zone between the two countries

Minutes before the plane was shot down, Syria’s state-run Al-Ikhbariya TV was broadcasting footage from the fence demarcating the UN buffer zone between Syrian and Israeli forces inside the Golan Heights. A UN observer post could be seen just on the other side of the fence.

The camera showed an Israeli post 400 meters (440 yards) away.

“Israel has a very clear policy: No plane, and certainly not a Syrian plane, is allowed to enter our airspace” without the appropriate authorization, Israel’s former Military Intelligence chief Amos Yadlin told Army Radio soon after Tuesday’s incident. “Any plane identified as an enemy plane is shot down,” he said.

In February of this year, the Syrian military shot down an Israeli F-16 fighter jet as it was taking part in a bombing raid against an Iranian-linked airfield in central Syria after an Iranian drone penetrated Israeli airspace, according to the IDF. The F-16’s pilot and navigator were injured as they bailed out of the aircraft, which crashed to ground in northern Israel.

Tuesday’s breach of Israeli airspace and the interception set off incoming rocket alert sirens throughout northeastern Israel, sending thousands of residents rushing to bomb shelters for the second day in a row.

Residents of northern Israel reported seeing white trails in the sky.

The Safed municipality told residents that air defense systems in the area had fired interceptor missiles and said there were no special safety instructions in light of the situation.

The alarms could be heard in the Golan Heights and Jordan Valley regions, the army said.

The sirens came a day after Israel launched two David’s Sling interceptor missiles at a pair of Syrian surface-to-surface missiles carrying approximately a half ton of explosives each that appeared to be heading toward Israel, but ultimately landed inside Syria. The Israeli interceptors did not strike the Syrian missiles: one was self-detonated by the IAF; the second reportedly fell to earth inside Syria.

The military’s air defense systems that detect and track incoming missiles and rockets are less accurate immediately after a projectile is launched, as they have less information on its trajectory. As the missile or rocket flies, the systems can better predict where it is likely to land.

Monday’s incident, which ultimately turned out to have been a false alarm, was the first known operational use of the David’s Sling system, which was declared operational last year.

The David’s Sling makes up the middle tier of Israel’s multi-layered anti-missile defense network.

In recent weeks, sirens in northern Israel have been triggered by the military shooting down unmanned aerial vehicles entering Israeli airspace from Syria.

On July 13, the Israeli military used an anti-aircraft Patriot missile to shoot down a Syrian army drone that was flying over the demilitarized zone separating Israel from Syria. Two days earlier, a Syrian military unmanned aerial vehicle penetrated some 10 kilometers (six miles) into Israeli territory before it too was shot down by a Patriot missile. The IDF said it had allowed the drone to fly so deeply into Israeli territory as it was not immediately clear if it belonged to the Russian military.

The Associated Press contributed to this report.