Syria's information minister has said that Israeli air raids against three targets on the outskirts of Damascus "open the door to all possibilities".
Omran al-Zoubie's comments in Damascus on Sunday came after an emergency cabinet meeting organised to respond to what a Western source said was a new attack on Iranian missiles bound for Lebanon's Hezbollah.
Although Zoubie did not hint at a concrete course of action, he said it was Syria's duty to protect the state from any "domestic or foreign attack through all available means".
He claimed the Israeli attacks were evidence of the country's links with "Islamic extremist groups" trying to topple the Syrian government.
Israel declined to confirm the attack so as not to pressure the Syrian President Bashar al-Assad into serious retaliation, according to a confidant of Benjamin Netanyahu, the Israeli prime minister.
Sunday's attack is the third Israeli assault this year on Syrian soil.
On the same day, Israel deployed two batteries of its Iron Dome rocket defence system to the north of the country. It described the action as part of "ongoing situational assessments".
Previous raids on Syria by Israel - which commands one of the most advanced militaries in the world and is backed by the US - have not elicited a military response from Syria or its allies Iran and Hezbollah.
Israeli fighter jets struck areas in and around Damascus, setting off a series of explosions, officials and activists said.
In-depth coverage of escalating violence across Syria
The attack, the second in three days and the third this year, signalled a sharp escalation of Israel's involvement in Syria's civil war.
Syrian state media reported that Israeli missiles struck a military and scientific research centre near Damascus and caused casualties.
Syria's government called the attacks against its territory a "flagrant violation of international law" that have made the Middle East "more dangerous".
A senior Israeli official, who spoke on the condition of anonymity, confirmed that Israel launched an air attack in Damascus early on Sunday.
The targets were reportedly the Jamraya military and scientific research centre near Damascus; a Syrian Republican Guard base is located nearby.
The target was Fateh-110 missiles, which have precision guidance systems with better aim than anything Hezbollah is known to have in its arsenal, the official told the Associated Press news agency.
Dilemma for regime
While the Assad government tried to use the air attacks to taint the rebels by linking them to Israel, the attacks still pose a dilemma for a regime already battling a relentless rebellion at home.
If it fails to respond, it looks weak and opens the door to such air strikes becoming a common occurrence.
But any military retaliation against Israel would risk dragging Israel and its powerful army into a broader conflict.
The tempo of the new raids added a dangerous dynamic to the conflict,causing concern that events could spin out of control and lead to a regional crisis.
Earlier, Syria's foreign ministry accused Israel of working with "terrorist groups".
"The blatant Israeli aggression against military sites in Syria confirms the coordination between Israel and terrorist groups and the takfiris of Jabhat al-Nusra, which is a branch of Al-Qaeda," the ministry said in a letter to the UN.
The ministry said the support was intended to boost "terrorist groups after the failure of their recent attempts to achieve control on the ground."
The Israeli raids were strongly condemned by Egypt as a "violation" of international law while the Cairo-based Arab League demanded the UN Security Council intervention to stop such Israeli attacks.