Over the past few years, the Israeli military has launched sporadic attacks against various targets on Syrian soil, in assaults slammed by Syria as attempts to boost the terror groups wreaking havoc on the country.
The London-based watchdog said the fate of the crew members is still unknown, adding that the chopper crashed in the southwestern countryside of the capital Damascus.
"In the past, Israel has reportedly carried out attacks against Syrian convoys and installations, in order to prevent Syria from transferring sophisticated weapons to Iran's local proxy Hezbollah", the Jerusalem Post reported Saturday.
The battles have been raging in the past 72 hours in the area, the watchdog added.
According to the reports, at least one missile hit the base situated near El-Kiswah, some 8 miles south of Damascus, while several others were intercepted by Syrian anti-aircraft missile systems.
According to foreign media reports, the Israeli fire was carried out from Lebanese airspace.
Last month the BBC revealed a claim that Iran was building a permanent military base near the town.
Russian Defense Minister Sergei Shoigu has told Israel that Moscow has agreed to expand a buffer zone along the Israeli-Syrian border, where Iranian and Hezbollah forces will not be allowed to enter.
Israeli security officials said the drone's operators had deliberately attempted to fly the aircraft across the Israeli border from Syria, but it was shot down without crossing into Israel.