Israeli warplanes struck several targets in Syria early Friday, prompting retaliatory missile launches, in the most serious incident between the two countries since the Syrian civil war began six years ago.
Israeli Prime Minister Benjamin Netanyahu said the strikes targeted weapons bound for Lebanon's Hezbollah, and that the Jewish State would do the same again if necessary.
Syria's military said it had downed an Israeli plane and hit another as they were carrying out pre-dawn strikes near the famed desert city of Palmyra that it recaptured from jihadists this month.
The Israeli military denied that any planes had been hit. The Syrian government has made similar unfounded claims in the past.
"The safety of Israeli civilians or the Israeli air force aircraft was at no point compromised," Israeli army spokesman Peter Lerner told AFP.
Netanyahu said in footage aired on Israel's major television networks: "When we identify attempts to transfer advanced weapons to Hezbollah and we have intelligence and it is operationally feasible, we act to prevent it.
"That's how it was yesterday and that's how we shall continue to act," he added.
"We are fully determined and the evidence of that it that we are acting. Everybody must take that into account -- everybody."
The Israeli air force said earlier that it had carried out several strikes on Syria overnight, but that none of the ground-to-air missiles fired by Syrian forces in response had hit Israeli aircraft.
It was an unusual confirmation by the Jewish state of air raids inside Syria.
"Overnight... aircraft targeted several targets in Syria," an Israeli army statement said.
"Several anti-aircraft missiles were launched from Syria following the mission and (Israeli) aerial defence systems intercepted one of the missiles," it said.
None of the missiles fired from Syria hit their targets, the army added.
One missile was intercepted by Israel's Arrow air defence system, Israeli media reported.
It would be one of the first times the system has been used.
A Jordanian military source said shrapnel from one missile fell in the north of the kingdom without causing any casualties.
- 'Significant shift' -
In April 2016, Netanyahu admitted for the first time that Israel had attacked dozens of convoys transporting weapons in Syria destined for Hezbollah, which fought a devastating 2006 war with Israel and is now fighting alongside the Damascus regime.
Israel does not usually confirm or deny each individual raid, but it may have been led to do so this time by the circumstances of the incident.
The missile fired from Syria prompted air raid sirens to sound in the Jordan Valley during the night, the Israeli army said.
Israel and Syria are still technically at war, though the border had remained largely quiet for decades until 2011 when the Syrian conflict began.
Assaf Orion, senior research fellow at Israel's Institute for National Security Studies, said Syria's response was a "significant" shift.
Until now, he said, when Israel attacked Hezbollah convoys there, it "usually went without a response or with an insignificant response from the Syrian side".
"(With this attack) the Syrian regime is trying to tell Israel it can't stand it any more and those actions will not be free of charge."
President Bashar al-Assad's position has been strengthened in recent months with his forces reclaiming all of Syria's second city Aleppo, as well as enjoying continuing Russian support.
Orion said the Syrian leader was feeling emboldened.
"He is saying: 'Don?t push me. I am not as weak as I used to be.'"
Yaakov Amidror, a former head of Israel's National Security Council, said weapons convoys of the Iran-backed Hezbollah remained a "red line" and that Israel would continue to attack them when deemed necessary.
The Arrow 3 interceptor, designed to shoot down ballistic missiles, was deployed to Israeli air force ground crews in January after successful testing by Israel and the United States.
Israel seized most of the Golan Heights from Syria in the 1967 Six-Day War and annexed it in 1981, in a move never recognised by the international community.
Israel pays close attention to developments in the Syrian conflict for fear that it could be exploited by its arch-rival Iran to instal allies close to the armistice line on the Golan and Israel's borders.