Israel conducted air raids against a Syrian missile base near the port city of Latakia on Thursday night according to a leak by an anonymous US administration official, speaking to CNN.
The US official said that Israel targeted missiles and related equipment out of fear that they would be transferred to Hezbollah.
It is unclear why the US would leak such information as it could put more pressure on Syria to retaliate against Israel.
The Syrian Observatory for Human Rights, which collates reports from opposition activists, said late on Wednesday that there had been an explosion at Syrian air defense base near Jableh, in the Mediterranean coastal province of Latakia.
The Latakia area is an Alawite stronghold, which also is the religion of Syrian President Bashar Assad.
"We're not commenting on these reports," a spokesman for the Israeli Defense Ministry said.
One Israeli official, speaking on condition of anonymity, said he thought that Israel had indeed carried out a strike. He stressed that he was not entirely certain, however.
Israel has repeatedly warned that it is prepared to use force to prevent advanced weapons, notably from Iran, reaching Hezbollah through Syria. It carried out several air strikes on Syria earlier this year.
The Lebanese national News Agency stated that Israeli fighter jets and reconnaissance planes entered Lebanese airspace Thursday morning and circled over Lebanon before returning to Israel.
Pan-Arab news outlet al-Arabiya reported on Thursday evening that Israel attacked two different targets in Syria on Wednesday: one target near the port city of Latakia and the other in Damascus.
Al-Arabiya quoted sources saying that the target of the alleged Israeli attacks were SA-8 surface to air missiles that were being delivered to Hezbollah. The missiles were destroyed completely according to the report.
Missiles fired from the Mediterranean sea targeted the air defense base near Latakia, according to Syrian opposition sources quoted by the report.