Israeli warplanes attacked a military research center in Damascus province at dawn Wednesday, Syria's military command said.

A senior U.S. official confirmed to NBC News that Israeli warplanes attacked Syrian military targets near Damascus. Syrian rebels disputed that, saying their forces had attacked the site. The reports did not have an immediate impact on oil prices or the stock market.

Regional security officials said Israel had been planning in the days leading up to the airstrike to hit a shipment of weapons bound for Hezbollah, Lebanon's most powerful military force and a sworn enemy of the Jewish state.

Among Israeli officials' chief fears is that Syrian President Bashar Assad will pass chemical weapons or sophisticated anti-aircraft missiles to Hezbollah -- something that could change the balance of power in the region and greatly hinder Israel's ability to conduct air sorties in Lebanon.