Syria has threatened to retaliate for an Israeli air attack while its ally Iran says there will be repercussions for Israel over the attack.

Ali Abdul-Karim Ali, the Syrian ambassador to Lebanon, said in Damascus on Thursday that Syria "has the option and the capacity to surprise in retaliation".

Ali said he could not predict when Syria would retaliate. It was up to the relevant authorities to prepare the retaliation and choose the time and place, he told Al Ahad, a website of Hezbollah, the Lebanese group closely allied with Syrian President Bashar al-Assad and Iran.

It is unclear what the exact nature of the target of Wednesday's Israeli air raids was.

Syrian state media said the attacks targeted a military research centre near the Syrian capital, while regional security sources told the Reuters and AP news agencies that the target was a convoy of lorries allegedly carrying anti-aircraft missiles for Hezbollah in Lebanon.

The Syrian military has denied the existence of any weapons shipment.

In Iran, the semi-official Fars news agency quoted Hossein Amir Abdollahian, Iran's deputy foreign minister, as saying the raid on Syria will have significant implications for Israel.

Ali Akbar Salehi, Iran's foreign minister, condemned the Israeli raid on state television, calling it a clear violation of Syria's sovereignty.

Iran is Syria's strongest ally in the Middle East, and has provided Assad's government with military and political backing for years.

Official complaint

Later on Thursday, Syria complained to the UN over the Israeli strike.

Although Israel and Syria are technically still at war, the ministry's official complaint evoked a 1974 disengagement agreement between the neighbours, state news agency SANA said.

"The Ministry of Foreign Affairs has summoned Iqbal Singha, commander of the UN Observer Disengagement Observer Force... and informed him of an official protest over the Israeli violation of the disengagement agreement of 1974," the ministry said.

The ministry said Israel "and the states that protect it at the UN Security Council" are responsible for the air strike, and "affirms Syria's right to defend itself and its territory and sovereignty".

The ministry called on "all the competent UN bodies to take the necessary steps given this grave Israeli violation, and to guarantee that it will not happen again".

The ministry denounced "the failure of the Security Council to take responsibility to prevent this grave Israeli attack, which poses serious threats to stability in the Middle East and security in the world".

'Barbaric aggression'

In a statement, Hezbollah condemned the attack as "barbaric aggression", saying it "expresses full solidarity with Syria's command, army and people."

Hezbollah did not mention any convoy but said the raid aimed to prevent Arab and Muslim forces from developing their military capabilities.

Russia, Syria's strongest international ally, said the Israeli raid appeared to be an unprovoked attack on a sovereign nation.

It said it was taking "urgent measures to clarify the situation in all its details".

"If this information is confirmed, we have a case of unprovoked attacks on targets in the territory of a sovereign state, which grossly violates the UN charter and is unacceptable," Russia's foreign ministry said in a statement.

"Whatever the motives, this is not justified."