Assad almost gave up his grip on power as the Islamic State group militants closed in on his official residence during the ongoing conflict, the conservative agency quoted a member of Iran's influential Expediency Discernment Council as saying.

"The martyr [Hossein] Hamadani told Assad that he should not worry, and that he should allow the distribution of weapons to 10,000 civilians to keep the threat at bay after they are organised," Ali Agha Mohammadi said, according to a translation by Syrian news site Zaman al-Wasl.

"Commander Hamedani recruited 80,000 Syrian militants, that with the intervention of Hizballah made the [Syrian] army stronger and today we see that the Syrian army was able to shoot down a Zionist aircraft," he added.

Former Revolutionary Guard commander Hossein Hamadani was killed in 2015 in the city of Aleppo by rebel forces.

Former Finnish president Martti Ahtisaari has said that in 2012 Russia proposed that Assad could cede power as part of a peace deal.

Ahtisaari said that the plan was ignored by the US, Britain and France because they were certain the autocrat would fall at that time when rebels seemed to be winning the war.

Iran, Russia, and Hizballah have all backed Assad's regime in the seven-year civil war, with Iran sending thousands of Revolutionary Guards and Shia militants to bolster Damascus' depleted forces.

Rebels have long demanded that Assad must step down before any peace deal can be reached.

Israel issued stark warnings on Sunday over Iran's presence in neighbouring Syria after a confrontation threatened to open a new and unpredictable period in the conflict.

Israel carried out major air raids in Syria on Saturday, including against what it described as Iranian targets - the first time it had publicly acknowledged doing so since the war began.

The raids came after an Israeli F16 fighter was shot down by Syrian air defences. The pilots survived, but it was Israel's first loss of a warplane in battle since 1982.

Other Israeli ministers spoke of refusing to accept Iran entrenching itself militarily in Syria, as Netanyahu has said repeatedly. Tehran denies it is doing so.