Q&A: Israeli strikes on Syria
Israel has carried out two attacks in two days on Syrian targets - three since the beginning of this year - raising the prospect of its deeper involvement in Syria's civil war.
What happened in the most recent attacks?
The Lebanese military complained of multiple overflights in their airspace by Israeli warplanes on Friday 3 May. Later that day unnamed US officials began briefing media outlets that Israeli jets had hit targets in Syria. Reports said the targets were sophisticated weapons heading towards Lebanon, where they would be delivered to Israel's arch-enemy, Hezbollah.
Syrian officials said nothing about the attack, and there was little verifiable information.
In the early hours of 5 May, Damascus was shaken by a number of explosions. Residents told the BBC the blasts were the most powerful to hit Damascus since the start of the country's civil conflict in 2011.
Syrian state media accused Israel of launching rocket attacks on the Jamraya scientific research institute. Some Western experts have said the institute is involved with chemical-weapons research.
However, unnamed Western and Israeli security officials briefed later that the target was not Jamraya. It was once again weapons caches heading to Hezbollah, which may have been stored near the research facility.
There was a similar disparity in the accounts of the last time Israel launched strikes on Syrian territory on 30 January. At that time, Syria denied the existence of any weapons convoys and said the research facility was the real target.
What has Israel said?
Israel has not formally acknowledged it carried out any of the strikes. On 3 February Ehud Barak, who was then the defence minister, hinted that his government was behind the January strike by saying the raid was "proof that when we say something we mean it".
He added: "We don't think [Syria] should be allowed to bring advanced weapons systems into Lebanon."
Other references to the strikes have come from unnamed officials or military sources quoted in US and Israeli media.
After the 5 May attack unnamed Israeli officials confirmed the assault and said the target was a shipment of Fateh-110 missiles, which were being transported from Iran to Lebanon via Syria.
Why would Israel attack?
Taken at face value, the statements from unnamed officials suggest Israel's actions are defensive. It fought a war with Hezbollah in 2006, and regards the Lebanese militant group as its key regional enemy. On this analysis, cutting the supply line to Hezbollah is crucial to stop a potential conflict.
Israel also has its own dispute with Syria over the Golan Heights. Although the border has been relatively peaceful, concern is growing that increasing chaos in Syria could spill over.
An added concern is that the Syrian regime allegedly has stockpiles of chemical weapons and sophisticated conventional weapons. Israeli military intelligence is thought to be monitoring the area via satellite for any movement of weapons outside Syria's borders.
The risks of carrying out strikes are huge. The attacks, if proved, would be likely to breach international law and could lead to retaliation.
Also, Israel risks becoming a major factor in Syria's civil war. The Assad regime has already portrayed anti-government rebels and Israel as working "hand in glove". And the strikes have brought a chorus of disapproval from the wider region, further shoring up Mr Assad's position.
Has Israel carried similar strikes before?
This year's strikes are the first inside Syria since September 2007, when Israeli warplanes were suspected of destroying a site that UN monitors said was likely to have been a nuclear reactor. Syria denied the claim, saying the building was a non-nuclear military site.
Israel never admitted the attack, and analysts say the ambiguity allowed Damascus to withstand any pressure to retaliate.
In 2006, Israeli jets flew over Mr Assad's presidential palace in a show of force after Syrian-backed Hamas militants in Gaza captured an Israeli soldier. And in 2003, warplanes attacked what Israel described as a training camp for Palestinian militants near Damascus. Syria vowed to retaliate for both attacks, but never did.