Israel says it has shot down a Syrian warplane which entered its airspace - a rare incident between the two foes.
In the Israeli-annexed Golan Heights, smoke rises above buildings across the border in Syria during air strikes. Photo: AFP
Two surface-to-air missiles were fired at the Sukhoi fighter jet, the Israel Defense Forces (IDF) tweeted.
However, Reuters reported the pilot of the plane, which crashed in Islamic State-held Syrian territory near the Israeli-occupied Golan heights, was actually killed in the crash, a non-Syrian source close to Damascus.
Syrian news agency Sana said Israel had targeted the jet over Syrian airspace, but did not say whether it was hit.
Sana quoted an unnamed military source as saying the plane was conducting raids against "armed terrorist groups" near the southern Yarmouk Valley.
Syria routinely describes rebel groups as terrorists.
Israel's Haaretz news website said residents in northern Israel saw interceptor missiles fired and heard explosions.
Flames and smoke were also later seen rising from the area of the fence between Syria and the Israeli-occupied Syrian Golan Heights, AFP news agency reports.
In a statement after the incident, the IDF said it was on "high alert" following "an increase in the internal fighting in Syria" and greater activity by Syria's air force in the region.
It said the fighter jet infiltrated about 2km into Israeli airspace before it was intercepted by Patriot missiles.
An Israeli military spokesman said the plane had crashed "most likely in the southern part of the Syrian Golan Heights". About a third of the Golan Heights is still nominally controlled by Syria.
Israel considers the occupied Golan Heights, and the airspace above it, as Israeli sovereign territory, though this is not recognised internationally. It has occupied the area since the 1967 Middle East war.
Israeli Prime Minister Benjamin Netanyahu said Syria had committed a "blatant violation" of the 1974 ceasefire agreement.
It is reportedly the first time Israel has shot down a manned Syrian aircraft since 2014.
Israel is not directly involved in the Syrian war but has attacked drones which have entered its airspace, and carried out dozens of air strikes on Syrian and Iranian military assets in Syria in recent years.
The incident comes just a day after Israel deployed its David's Sling missile defence system - designed for use against medium-range missiles - for the first time.
The system was activated "in response to the threat" from two Syrian surface-to-surface missiles approaching Israeli territory, an army statement said.
Israel has repeatedly warned it will not tolerate any Syrian breach of the 1974 ceasefire deal which delineated the lines of separation between the two sides' forces on the Golan Heights.
-BBC / Reuters