JERUSALEM (AFP) - Israel was silent on Saturday on US media reports that it launched new air strikes on Syria targeting a weapons shipment to the Lebanese militant group Hizbollah.
The Israeli military and spokesmen for the defence ministry and prime minister's office declined to comment on the reports.
Israel and Hizbollah, a faithful ally of Syrian President Bashar al-Assad, fought a devastating war in the summer of 2006.
CNN television said US and Western intelligence agencies were reviewing information suggesting Israel conducted a strike overnight on Thursday.
A diplomatic source in Lebanon told AFP the operation destroyed surface-to-air missiles recently delivered by Russia that were being stored at Damascus airport.
US President Barack Obama said Israel is justified in protecting itself against shipments of advanced weapons to Hezbollah, without commenting directly on the reported strike.
"The Israelis justifiably have to guard against the transfer of advanced weaponry to terrorist organisations like Hizbollah," he told Spanish-language Telemundo television during a trip to Mexico and Central America.
Lebanon's army said in a statement that pairs of Israeli airplanes entered Lebanese airspace three times overnight, staying in Lebanese airspace for two to three hours at a time.
US media reported that Washington does not believe Israeli warplanes entered Syrian airspace to conduct the strikes.
A senior US official told NBC News that the air strikes were probably tied to delivery systems for chemical weapons.
But a senior Israeli defence official flatly rejected the notion that Hizbollah even wanted chemical weapons.
Mr Amos Gilad said the militant Shi'ite group "is not eager to get its hands on those (chemical) arms. It is eager to take weapons systems like rockets." "With chemical weapons it has problems," he said in remarks at a public event, relayed by Israeli media. "Chemical weapons can kill those who don't know how to use it too."
"I want to calm everyone here. Hizbollah doesn't have chemical weapons," he told the audience.
Pentagon officials declined to comment on the air strike reports.
But Republican Senator Lindsey Graham of South Carolina, who serves on the Senate Armed Services Committee, was quoted as telling an audience that Israel had indeed bombed Syria.
"Israel bombed Syria tonight," Mr Graham was cited by the Politico news website as saying in passing, without offering any further details.
The Israeli military on Saturday declined comment and a defence official said only that the Jewish state was monitoring any possible transfer of chemical weapons.
Israel is "following the situation in Syria and Lebanon, with an emphasis on transferring chemical weapons and special arms," the official told AFP.
If confirmed, this would be the second Israeli air strike on Syria this year.
Earlier this month, Israel implicitly admitted carrying out a January raid on a weapons convoy in Syria thought to be en route to Hizbollah.