The Russian military opened fire on Israeli jets with advanced S-300 anti-aircraft missiles after an alleged Israeli strike on Iranian targets in northwestern Syria last Friday, Israeli media reported Monday.

The Israeli Air Force attacked several targets near the city of Masyaf in northwestern Syria. Five people died in the ensuing response, Syria’s state news agency said.

The Syrian military fired rounds of anti-aircraft missiles, which have been mostly ineffective at stopping Israeli strikes against arms caches and other Iranian-linked sites, according to the Times of Israel.

However, this time the S-300 batteries, which are operated by Russian forces, opened fire as the aircraft were leaving the area.

The unprecendented event could signal a significant shift in Moscow’s position on Israel.

As an ally of both Russia and Ukraine, Israel has been cautious about taking sides in the war. Russia has heavy military presence in Syria and controls its skies and as such, Jerusalem coordinates all military strikes on Iranian targets in Syria with Moscow.

Israeli Defense Minister Benny Gantz on Monday said Israel would continue to stop Iran from achieving “advanced capabilities” in Syria, but did not mention the alleged Russian strike.

“The State of Israel will continue to act against any enemy that threatens it, and prevent the transfer of advanced capabilities from Iran that endanger the citizens of Israel and harm the stability of the entire region,” Gantz said.