BEIRUT // Israel carried out its second air strike in days on Syria early on Sunday, a Western intelligence source said, in an attack that shook Damascus with a series of powerful blasts and drove columns of fire into the night sky.
Israel declined to comment, but Syria accused its neighbour of carrying out a raid on a military facility just north of the capital.
The explosions came soon after an Israeli official said his country had carried out an air strike earlier in the week targeting missiles in Syria intended for the Lebanese militant group Hizbollah.
The target of Sunday's attack, according to Syrian media, was the same Jamraya military research centre which was hit by Israel in another assault in January. Jamraya, on the northern approaches to Damascus, is just 15km from the Lebanese border.
Video footage uploaded onto the internet by activists showed a series of explosions. One lit up the skyline over the city, while another sent up a tower of flames and secondary blasts.
The Western intelligence source said Israel carried out the attack and the operation hit Iranian-supplied missiles which were en route to Hizbollah.
"In last night's attack, as in the previous one, what was attacked were stores of Fateh-110 missiles that were in transit from Iran to Hizbollah," the source said.
The British-based Syrian Observatory for Human Rights said the scale of the attack meant it was beyond the military capability of Syrian rebels, and quoted eyewitnesses in the area as saying they saw jets in the sky at the time of the blasts.
The Observatory said the blasts hit Jamraya as well as a nearby ammunition depot. Other activists said a missile brigade and two Republican Guard battalions may also have been targeted in the heavily militarised area just north of Damascus.
Syria's state television said the strikes were a response to recent military gains by President Bashar Al Assad's forces against rebels. "The new Israeli attack is an attempt to raise the morale of the terrorist groups which have been reeling from strikes by our noble army," it said.
Reports by activists and state media are difficult to verify in Syria because of restrictions on journalists operating there.
If confirmed, Sunday's attack would be Israel's third strike inside Syria since late January, but there was no immediate comment from Israeli officials.
Israel has repeatedly made clear it is prepared to use force to prevent advanced weapons from Syria reaching Lebanon's Shiite Hizbollah guerrillas, who fought a 34-day war with Israel in 2006. Mr Al Assad and Hizbollah are allied to Iran, Israel's archenemy.
Uzi Rubin, an Israeli missile expert and former defence official said the Fateh-110 missile "is better than the Scud, it has a half-ton warhead". Iran has said it adapted the missile for anti-ship use by installing a guidance system, he added.