The Israeli military confirmed one of its fighter jets crashed on Saturday after coming under Syrian anti-aircraft fire following a raid targeting Iranian facilities in Syria.
The F-16 jet crashed in the Israeli-held Golan Heights, with the two pilots ejecting successfully and landing by parachute.
The Israeli military said early assessments indicated the jet had been shot down by Syrian fire, but that the cause of the crash was still unconfirmed.
Syria said its systems downed the jet, while Lebanon's Hezbollah said it marked the "start of a new strategic phase" which will limit Israeli incursions into Syrian airspace.
Israel conducted heavy air strikes in Syria on Saturday after a drone by Iran-backed force was launched into its airspace from Syria.
Israeli aircraft have struck 12 Syrian and Iranian targets in Syria, including an aerial defence system, the IDF said. It claims to have received confirmation that hits on an Iranian control facility were accurate.
"During the attack, anti-aircraft missiles were fired towards Israel, triggering alarms that were heard in Northern Israel," according to the military.
Iran denied dispatching the drone or any involvement in the downed fighter jet.
"Reports of downing an Iranian drone flying over Israel and also Iran's involvement in attacking an Israeli jet are so ridiculous," Iranian state TV quoted foreign ministry spokesman Bahram Qasemi as saying.
Israeli incursions into Syria have been common since the start of the civil war in 2011, but the downing of one of its fighter jets is said to represent a serious escalation.
Syrian state media said Syrian air defences were responding to a "new Israeli aggression", with Syrian TV reporting sounds of explosions in the Damascus countryside on Saturday morning.