Ammon News - BEIRUT (Reuters) - Heavy explosions shook Damascus early on Sunday and Syrian state television said Israeli rockets had struck a military research center on the outskirts of the capital.

The research center in Jamraya was the target of an earlier Israeli strike in January. Video footage uploaded onto the Internet by activists showed a huge ball of fire rising into the night sky.

On Friday, Israel has carried out an air strike into Syria, targeting a shipment of missiles bound for Hezbollah guerrillas in neighbouring Lebanon, an Israeli official said.

The Jewish state has made clear it is prepared to resort to force to prevent advanced Syrian weapons, including President Bashar al-Assad's reputed chemical arsenal, reaching his Hezbollah allies or Islamist rebels taking part in a more than two-year-old uprising against his government.

The target of Friday's raid was not a Syrian chemical weapons facility, a regional security source earlier told Reuters on condition of anonymity.

A US official, who also declined to be identified, had told Reuters on Friday the target was apparently a building.

The attack took place after Prime Minister Benjamin Netanyahu's security cabinet approved it in a secret meeting on Thursday night, the security source said.

CNN quoted unnamed US officials as saying Israel most likely conducted the strike "in the Thursday-Friday time frame" and its jets did not enter Syrian air space.

The Israeli air force has so-called "standoff" bombs that coast dozens of kilometres across ground to their targets once fired. That could, in theory, allow Israel to attack Syria from its own turf or from adjacent Lebanon.

Lebanese authorities reported unusual intensive Israeli air force activity over their territory on Thursday and Friday.

A Lebanese security source said his initial impression was that Israeli overflights were monitoring potential arms shipments between Syria and Lebanon, potentially to Hezbollah, a militant Shi'ite Muslim ally of Iran and Assad.