"Our air defences are countering hostile missiles coming from the sea towards the city of Latakia, and a number of them have been intercepted," the source said.

That came shortly after the official SANA news agency reported "aggression on Latakia targeting a technical industries institute", without providing further information.

Syrian state television broadcast scenes that showed a dark night sky lit up by a flashes of light lasting several minutes.

Head of the Syrian Observatory for Human Rights Rami Abdel Rahman told AFP that "violent explosions were caused by missiles targeting ammunition depots in the technical industries institute".

He said the site on the eastern outskirts of Latakia belonged to government forces, but added it was unclear whether the depots were being used by regime troops or those of key ally Iran.

The Syrian government regularly accuses Israel of targeting its military positions.

On Saturday an Israeli missile attack targeted Syria's capital airport, SANA said, activating air defences which shot down a number of the projectiles.

Syrian state media on September 4 said its air defences had downed several Israeli missiles in the coastal province of Tartus and in central Hama.

This month, Israel acknowledged having carried out more than 200 strikes in war-ravaged Syria over the past 18 months, mainly against Iranian targets.

It has also admitted to striking Syria to prevent what it says are deliveries of advanced weaponry to Lebanon's Hezbollah militia, which fights alongside Syrian troops and is an arch-foe of Israel.

Syria's conflict erupted in 2011 and has since killed more than 360,000 people, with millions more displaced internally and to neighbouring countries.