The Israeli military said it has shot down a Syrian fighter jet that entered its airspace.
The advance of the Syrian Sukhoi fighter jet was monitored on Tuesday before the Israeli military shot it down with a pair of Patriot missiles after it entered Israeli airspace by about two miles.
It is only the second such incident along the border in 30 years.
The military said there had been an increase in the internal fighting in Syria since the morning hours, including an increase in the activity of the Syrian air force.
Israeli forces said they are on high alert and would continue to protect Israeli territory.
Syrian forces have been battling rebels and Islamic State militants at the frontier with Israel in recent weeks.
Tuesday marked the first time Syrian government forces reached the border fence with the UN’s Disengagement Observer Force at the edge of the Israeli-occupied Golan Heights.
An Israeli military spokesman said the plane departed from the Syrian T4 air base, which Israel is believed to have attacked earlier this year.
Lt Col Jonathan Conricus said that the plane flew toward Israel at “relatively high speed” before breaching the country’s airspace.
He said it is not known if the plane deliberately crossed into Israel, and the fate of the pilot is also unknown.
The plane crashed in the southern part of the Syrian Golan Heights, he said.
Lt Col Conricus said the increased activity near Israel’s frontier with Syria put the military on “elevated alert” and prompted Israel to issue a number of warnings through different channels to ensure a 1974 agreement which sets out a demilitarised zone along the shared Syria-Israel frontier would not be violated.
It is the first time Israel has shot down a Syrian jet in four years.
The military captured the Golan Heights from Syria in 1967, with the UN deploying a peacekeeping force between the two sides in 1974.
It is the first time government forces have taken up positions along the frontier since an uprising against Syrian president Bashar Assad swept through the country in 2011.
Islamic State militants later seized territory from rebels along the frontier region.