BEIRUT (AP) -- Syria threatened Thursday to retaliate for an Israeli airstrike and its ally Iran said the Jewish state will regret the attack.
Syria sent a letter to the U.N. Secretary-General stressing the country's "right to defend itself, its territory and sovereignty" and holding Israel and its supporters accountable.
"Israel and those who protect it at the Security Council are fully responsible for the repercussions of this aggression," the letter from Syria's Foreign Ministry said.
U.S. officials said Israel launched a rare airstrike inside Syria on Wednesday targeting a convoy carrying anti-aircraft weapons bound for Hezbollah, the powerful Lebanese militant group allied with Syria and Iran.
In Israel, a lawmaker close to hard-line Prime Minister Benjamin Netanyahu stopped short of confirming involvement in the strike. But he hinted that Israel could carry out similar missions in the future.
The attack has inflamed regional tensions already running high over Syria's 22-month-old civil war.
Israeli leaders in the days leading up to the airstrike had publicly expressed concern that Syrian President Bashar Assad may be losing his grip on the country and its arsenal of conventional and nonconventional weapons.
The Syrian military denied there was any such weapons convoy. It said low-flying Israeli jets crossed into the country over the Israeli-occupied Golan Heights and bombed a scientific research center. The facility is in the area of Jamraya, northwest of Damascus. and about 15 kilometers (10 miles) from the Lebanese border.
A U.S. official said the airstrike targeted trucks containing sophisticated Russian-made SA-17 anti-aircraft missiles. The trucks were next to the military research facility identified by the Syrians, and the strike hit both the trucks and the facility, said the official, who spoke on condition of anonymity because he was not authorized to speak about the operation.
If the SA-17s were to have reached Hezbollah, they would have greatly inhibited the Israeli air force's ability to operate in Lebanon, where Israel has flown frequent sorties in recent years.
Maj. Gen. Abdul-Aziz Jassem al-Shallal, who in December became one of the most senior Syrian army officers to defect, told The Associated Press by telephone from Turkey that the targeted site is a "major and well-known" center to develop weapons called the Scientific Research Center.
Al-Shallal, who until his defection was commander of the military police, said no chemical or nonconventional weapons are at the site. He added that foreign experts, including Russians and Iranians, are usually present at such centers.
Syrian Ambassador to Lebanon Ali Abdul-Karim Ali threatened retribution for the Israeli airstrike, saying Damascus "has the option and the capacity to surprise in retaliation."
He told Hezbollah's al-Ahd news website that it was up to the relevant authorities to prepare the retaliation and choose the time and place.
The Syrian Foreign Ministry summoned Major-General Iqbal Singh Singha, the head of mission and force commander for United Nations Disengagement Observer Force (UNDOF) on the Golan Heights, to complain about the Israeli violation.
The force was established in 1974 following the disengagement of Israeli and Syrian forces in the area and has remained there since to maintain the cease-fire. Israel captured the Golan, a strategic plateau, from Syria in the 1967 Middle East war.
At U.N. headquarters in New York, deputy U.N. spokesman Eduardo del Buey said: "UNDOF did not observe any planes flying over the area of separation, and therefore was not able to confirm the incident." UNDOF also reported bad weather conditions, he said.
Hezbollah condemned the attack as "barbaric aggression" and said it "expresses full solidarity with Syria's command, army and people."
The group did not mention any weapons convoy in the statement but said the strike aimed to prevent Arab and Muslim forces from developing their military capabilities.
In Iran, the country's top nuclear negotiator, Saeed Jalili, said "the Zionist regime will regret its aggression against Syria," Iran state television said.
The semi-official Fars news agency quoted Deputy Foreign Minister Hossein Amir Abdollahian as saying the raid will have significant implications for Israel.
Iranian Foreign Minister Ali Akbar Salehi condemned the airstrike on state television, calling it a clear violation of Syrian sovereignty. Iran is Syria's strongest ally in the Middle East, and has provided Assad's government with military and political backing for years.
Russia, Syria's most important international ally, said this appeared to be an unprovoked attack on a sovereign nation. Moscow 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 U.N. Charter and is unacceptable," Russia's Foreign Ministry said in a statement. "Whatever the motives, this is not justified."