Iran has backed Syria's "right to defend itself" after Israel launched strikes on what it said was Iranian military infrastructure inside Syria.
In the first comments by Iran since Thursday's wave of strikes, the foreign ministry condemned the "blatant violation of Syria's sovereignty".
The strikes were the heaviest carried out by Israel on Syria in decades.
They came after 20 rockets were fired at Israeli military positions in the occupied Golan Heights.
Israel said Iranian fighters had carried out that attack. Iran has neither directly confirmed or denied this but has said that Israel's attacks on Syria were founded "on self-proclaimed, baseless pretexts".
Iran has deployed hundreds of troops in Syria, ostensibly as military advisers to the Syrian military. Thousands of militiamen armed, trained and financed by Iran have also been battling rebel forces alongside Syrian soldiers.
On Thursday, in response to the Golan Heights attack, Israel said its fighter jets had struck almost all of Iran's military infrastructure inside Syria – some 70 targets – in its biggest assault since Syria's civil war started in 2011.
Iran and Israel are enemies but have never fought a direct war.
Foreign ministry spokesman Bahram Qasemi was quoted on Iranian state TV as saying: "Iran strongly condemns… [Israel’s] attacks on Syria. The international community's silence encourages Israel's aggression. Syria has every right to defend itself."
Mr Qasemi said Israel "cannot stand peace and stability in the region and sees its own safety in making the region all the more unstable".
He said Israel's "baseless pretexts amount to a blatant violation of Syria's sovereignty and goes against all international conventions".
He did not refer to Iran's military presence inside Syria.
Mr Qasemi said the attacks were an attempt by international supporters of rebel groups fighting Syrian President Bashar al-Assad to shore them up after their "many failures" and to try to "tip the scales in their favour".
The Syrian government, backed by Iran and Russia, has made significant gains over the rebel groups in the past year.
A defiant Prime Minister Benjamin Netanyahu said on Thursday that Iran had "crossed a red line" and Israel's action "was a consequence" of that.