American officials says Israeli warplanes have struck a military base near the Syrian city of Latakia.
Latakia is a port city about 330km from the capital Damascus.
An explosion at a missile storage site in the area was widely reported in the Israeli press, but an attack has not been confirmed by the Israeli government, CNN reports.
The target, according to a US administration official who spoke to CNN, was missiles and related equipment the Israelis felt might be transferred to the Lebanon-based militant group Hezbollah.
CNN reports that the official declined to be identified because of the sensitive nature of the information.
Israel has been accused several other times this year of launching airstrikes inside Syria, including once in January. In the January incident, a US official said Israeli fighter jets bombed a Syrian convoy suspected of moving weapons to Hezbollah.
Israel's military did not comment on any of the allegations at the time, but has long said it would target any transfer of weapons to Hezbollah or other groups designated as terrorists, as well as any effort to smuggle Syrian weapons into Lebanon that could threaten Israel.
Hezbollah, a Shiite Muslim militant group, has been helping Syrian government forces led by Bashar al-Assad, a member of the Shiite offshoot Alawite sect; the rebels and other militants fighting al-Assad's forces and Hezbollah are largely made up of Sunni Muslims.
Syrian civil war began in March 2011 after government forces cracked down on protesters during the Arab Spring movement,
The United Nations estimates that more than 100,000 people have died in the conflict.