(Reuters) - Israel shot down a pilotless plane over the Golan Heights on Tuesday and said it was probably an Iranian-built aircraft on a reconnaissance mission for the Lebanese Hezbollah militant group along Israel's frontier with Syria.

The incident came hours before Prime Minister Benjamin Netanyahu was due to address the U.N. General Assembly and cite Israeli concerns about an entrenchment in Syria of Iranian and Hezbollah forces that have been helping Damascus beat back Islamist-led rebels.

The drone was launched from an air base near Damascus and was downed with a Patriot interceptor missile over the Golan demilitarized zone that has separated Israeli and Syrian forces since the ceasefire deal that followed their 1973 war, the military said.

"As we understand, it was on a reconnaissance mission along the border and the Golan Heights on behalf of Hezbollah," a military spokesman, Lieutenant-Colonel Jonathan Conricus, told reporters. "Our intelligence suggests it was ... Iranian-made."

Asked whether the drone might have been armed, Conricus said that information was not yet available. He said Israeli warplanes had also been scrambled.

Officials from Syria, Hezbollah and Iran had no immediate comment on the incident. The Golan, which Israel captured from Syria in the 1967 conflict, has seen spillover violence from the Syrian civil war. Israel has at times fired to foil what it deemed deliberate cross-border attacks.

"Our message is: The IDF (Israel Defense Forces) will not allow any violation of Israeli sovereignty and we will not allow Iranian forces, Hezbollah, Islamic Jihad or Shi'ite militias of any kind to approach the Israeli borders," Conricus said.