The Israeli military has shot down a Syrian military aircraft that it said had infiltrated it airspace over the Golan Heights.

Tuesday's incident was the most serious incident to take place on the strategic plateau since the outbreak of the Syrian civil war in 2011.

The Israeli army radio said it was apparently a MiG-21 fighter jet which was shot down by a surface-to-air missile. The wreckage landed on the Syrian-controlled side of the plateau.

There was no official confirmation on the type of the aircraft.

Israel has largely stayed on the sidelines of Syria's civil war raging across the border, but its leaders appear increasingly nervous about the possibility of al-Qaeda-linked fighters occupying the Golan's high ground over northern Israel.

The Syrian state TV quoted a military source saying the downing of the plane, which coincided with US attacks on the ISIL group in Syria, came "in the framework of [Israel's] support for the terrorist [ISIL] and the Nusra Front".

Annexed territory

Since the uprising against President Bashar al-Assad started more than three years ago, a growing number of rockets and mortar rounds have hit the Israeli side of the Golan.

Most are stray but there have been several incidents of intentional fire, one of which killed an Israeli teenager in June.

Israel seized 1,200sq km of the Golan Heights in 1967, then illegally annexed it in 1981.

About 510sq km remains on the Syrian side of the ceasefire line, with UN forces overseeing a buffer zone stretching about 70km from Lebanon in the north to Jordan in the south.