Growing evidence suggests that the Israeli Air Force carried out a secret mission in Syria Sunday night, targeting Russian-made missile launchers deployed by forces loyal to President Bashar Assad.

A few minutes before midnight, a number of regional news sources reported a loud explosion in the coastal town of Latakia, where the S-300 systems are thought to be located. Those reports came on the heels of Lebanese media describing sightings of Israeli aircraft in Lebanese airspace, which Israeli planes would have to cross in order to reach targets on the Syrian coastal plain.

The final report on the incident, issued by the NNA Lebanese Ministry of Information website, was published on Monday morning.

“On Sunday at 10:45 p.m., two Israeli war planes violated Lebanese airspace off west Batroun, executed circular flight over the Lebanese regions; and then left at 11:55 p.m. off west Nakoura village," it read.

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For those who have been closely watching the bloody civil war in Syria, Assad's alliance with the Lebanese terror group Hezbollah, a sworn enemy of Israel, has been troubling. Israel allegedly ordered a similar mission in the fall.

“There is constant concern that the Assad regime will transfer advanced weaponry to Hezbollah,” retired Brigadier Gen. Shlomo Brom, a senior research associate at the Institute for National Security Studies in Tel Aviv, told FoxNews.com. "Assad has become so dependent on the assistance of Hezbollah and Iran, that the assumption in Israel is that it cannot say no when there is a demand from one of the parties to supply anything to Hezbollah.”

As usual, both Israeli and Syrian officials are remaining tight-lipped about the alleged targeting of the site. Israel has made it clear on numerous occasions that it will not allow the transfer of missiles from the Assad regime to Hezbollah under any circumstances.

Early in the Syrian civil war Israel warned of the danger of Syrian chemical weapons reaching the Iranian-backed Hezbollah. While the Syrian chemical stockpiles have reportedly been neutralized by inspection teams from the international community, highly dangerous conventional weapons such as the S-300 surface-to-air missile systems remain a big danger to Israel should they reach Hezbollah’s hands. Major Israeli cities such as Haifa, Tel Aviv and Jerusalem are believed to potentially be within range of a variety of Hezbollah missiles should hostilities break out between the two old enemies.

Hezbollah already has a reported 100,000 missiles of various ranges pointed at Israel despite the UN peacekeeping force (UNIFIL) having been charged since the end of the Israel-Hezbollah conflict in 2006 with ensuring that arms wouldn’t reach the internationally recognized terrorist organization.

The 2006 UNIFIL mandate, according to Security Council resolution 1701, clearly states that it must, “assist the Government of Lebanon, at its request, in securing its borders and other entry points to prevent the entry in Lebanon without its consent of arms or related materiel.” The mandate further states that UNIFIL should “...take all necessary action in areas of deployment of its forces and as it deems within its capabilities, to ensure that its area of operations is not utilized for hostile activities of any kind.”

In spring 2013, the reported delivery of the first batch of the S-300 system by Russia to Assad was seen by regional observers as a deliberate tactic by Moscow to deter the US and the West from an armed intervention in the Syrian civil war on the side of the anti-Assad forces. It is still unclear whether Russia has delivered all the parts for the system, but Brom clarified one significant aspect of the agreement between the two parties.

“The contract that the Assad regime concluded with Russia for supply of weaponry stated that Syria is not allowed to legally transfer it to a third party. The Russians prefer to play the game and behave as if this didn’t happen” Brom said.

Last July, Israeli Prime Minister Benjamin Netanyahu, in a face-to-face meeting with Russian President Vladimir Putin, reportedly made clear his position on the S-300 issue, spelling out his opposition to the weapons system reaching Syria. Two months earlier, according to Israel’s Ha’aretz newspaper, Yaakov Amidror, national security adviser to Netanyahu, made clear to European diplomats that Israel would “prevent the S-300 missiles from becoming operational.”

In November, the White House, to the chagrin of Israel, confirmed that Israel had targeted “missiles and related equipment” in an airstrike on Latakia. The U.S. leak caused uproar in Jerusalem and put significant strain on relations between the two allies. So far there has been no repeat of the U.S. comments with regard to the latest alleged Israeli operation.

Paul Alster is an Israel-based journalist who can be followed on twitter @ paul_alster and at www.paulalster.com