By Barbara Starr

A series of explosions on July 5 at a critical Syrian port was the result of airstrikes by Israeli warplanes, according to multiple U.S. officials.

Regional media widely reported the predawn explosions at Latakia, but no one had officially claimed responsibility.

Three U.S. officials told CNN the target of the airstrikes were Russian-made Yakhont anti-ship missiles that Israel believes posed a threat to its naval forces.

The officials declined to be named because of the sensitive nature of the information.

So far, the Israeli government has also declined to comment to CNN.

Israel's defense minister Moshe Yaalon denied involvement, according to one Israeli news site.

"It has been a long time that we are not intervening in Syria's bloody war. Red lines were presented and we maintain them," said Yaalon, according to YNet News. "There is an explosion here or an attack there, somewhere in the Middle East, most of the time they accuse us."

Israeli and U.S. intelligence are also watching closely for additional shipments of Russian arms to Syria from Russian warships located off the coast.

The United States believes some supplies, including ammunition and small arms, have been unloaded in recent weeks. So far, there has been no indication of heavy weapons or helicopters that the Syrian regime of Bashar al-Assad anticipates.

CNN has reported at least three previous Israeli airstrikes against Syrian targets in recent months in instances where it believed weapons were being transferred to Iranian backed Hezbollah fighters in Lebanon that could also threaten Israel.