An AFP correspondent in Damascus heard several large explosions before the official Sana news agency announced the defensive action.

"The aggression is still going on and the air defence is able to counter the targets, dropping most of them" in the south of the country, the agency said.

Since the beginning of the war in Syria in 2011, Israel has conducted hundreds of strikes in Syria, most of them against what it says are Iranian and Hezbollah targets.

Hezbollah is a Lebanese Shiite group that supports Syria's President Bashar al-Assad, who is also backed by Tehran.

Israel says it is determined to prevent its arch-foe Iran from entrenching itself militarily in Syria, where Tehran backs Assad's regime.

The Jewish state insists that it has the right to continue to target positions held by Iran and its ally Hezbollah out of self-defence.

The Syrian conflict has killed more than 370,000 people and drawn in world powers since it started with the brutal repression of anti-government protests.