Israel has carried out new air strikes on Syria, targeting a weapons shipment to Lebanese militant group Hezbollah, according to US officials cited by the media, but the Jewish state was silent on the claims on Saturday.
CNN television said US and Western intelligence agencies were reviewing information suggesting Israel conducted a strike overnight between Thursday and Friday.
Lebanon's army said pairs of Israeli airplanes entered Lebanese airspace on three occasions overnight between Thursday and Friday.
The first two entered over the souther city of Sidon at 7:10 PM (1610 GMT), followed three hours later by a second pair that entered over Jounieh, north of Beirut, a statement said.
The last pair flew in over the capital, the statement said, adding that the planes stayed in Lebanese airspace for two to three hours at a time.
CNN reported that the United States does not believe Israeli warplanes entered Syrian airspace to conduct the strikes.
A senior US official told NBC News that the airstrikes were likely tied to delivery systems for chemical weapons.
White House and Pentagon officials declined to comment on the 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," Graham was cited by the Politico news website as saying in passing, without offering any further details.
Israel was tightlipped on the claims, with the army declining on Saturday to comment and a defence official saying 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 mark the second time Israel has hit Syria this year.
Earlier this month, the Jewish state implicitly admitted carrying out a January air strike on a weapons convoy in Syria thought to be en route to Hezbollah -- a long-time Damascus ally.
The reports on the latest strike came shortly after President Barack Obama nearly ruled out deploying US troops to Syria, saying he did not foresee a scenario in which that would be beneficial to the United States or Syria.
Speculation has mounted that the Obama administration could reverse its opposition to arming the rebels after the White House said last week that President Bashar al-Assad likely used chemical weapons on his people.
Obama has been reluctant to intervene in the war but faces mounting criticism that he has allowed the Assad regime to cross his own declared "red line" on using chemical weapons.