The two pilots ejected and parachuted to safety in Israel. They were later taken to hospital.

Israel said its aircraft, an F-16 jet, was carrying out strikes in response to the launch of a drone into Israeli territory. The drone was intercepted.

Red alert sirens sounded in areas of northern Israel and the Golan Heights.

Residents reported hearing a number of explosions and heavy aerial activity in the area near Israel's borders with Jordan and Syria.

"A combat helicopter successfully intercepted an Iranian UAV [unmanned aerial vehicle] that was launched from Syria and infiltrated Israel," the military said in a statement.

The statement added that the drone was identified quickly and was "under surveillance until the interception".

"In response, the IDF [Israel Defence Forces] targeted Iranian targets in Syria," the military said.

Syrian state media reported that the country's air defences opened fire in response to an Israeli act of "aggression" against a military base on Saturday, hitting "more than one plane".

Israeli strikes in Syria are not unusual, the BBC's Middle East correspondent Tom Bateman says. But he adds that the downing of an Israeli fighter jet marks one of the most serious escalations yet.