BEIRUT/AMMAN: Syria protested to the United Nations Thursday over an alleged Israeli airstrike on its territory and warned of a possible “surprise” response.

The Foreign Ministry summoned the head of the U.N. force in the Israeli-occupied Golan Heights to deliver the statement a day after Israel hit what Syria said was a military research center and diplomats said was a weapons convoy heading for Lebanon.

Major-General Iqbal Singh Singha, the head of mission and force commander for United Nations Disengagement Observer Force, was informed about the Syrian complaint.

At the 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.

Syrian TV quoted the Foreign Ministry as saying it held “Israel and those who protect it in the Security Council fully responsible for the results of this aggression and affirms its right to defend itself, its land and sovereignty.”

The ministry said it considered Wednesday’s attack to be a violation of a 1974 military disengagement agreement and demanded the U.N. Security Council condemn it unequivocally.

U.N. Secretary-General Ban Ki-moon expressed “grave concern.”

Ban “calls on all concerned to prevent tensions or their escalation,” his office said, adding that international law and sovereignty should be respected.

In Beirut, Syria’s Ambassador to Lebanon Ali Abdel-Karim Ali said “the Israelis, and the United States behind them, along with their Arab and regional accomplices, realize that Syria, which defends its sovereignty and territory, may decide to respond by surprise to this aggression.” Ali was quoted by the Hezbollah-linked Lebanese website Al-Ahad.

While not confirming the targets of the Israeli air raid, the White House warned that Syria’s government should not transfer arms to Hezbollah.

“Syria should not further destabilize the region by transferring weaponry to Hezbollah,” said Ben Rhodes, a U.S. deputy national security adviser.

Rhodes, asked about Iranian and Syrian threats to retaliate against Israel, said that such rhetoric from Tehran showed how concerned leaders there were about the prospect of President Bashar Assad’s regime falling.

Israel has maintained total silence over the incident, just as it did in 2007 when it bombed a suspected Syrian nuclear site, an attack which passed without Syrian military retaliation.

Diplomats, Syrian rebels and security sources said Israeli jets had bombed a convoy near the Lebanese border, apparently hitting weapons destined for Hezbollah. Syria denied the reports, saying the target was a military research center northwest of Damascus and 13 km from the Lebanese border.

Hezbollah said Israel was trying to thwart Arab military power and vowed to stand by its ally. “Hezbollah expresses its full solidarity with Syria’s leadership, army and people,” said the group.

Russia said any Israeli airstrike would amount to unacceptable military interference. “If this information is confirmed, we are dealing with unprovoked attacks on targets on the territory of a sovereign country, which blatantly violates the U.N. Charter and is unacceptable, no matter the motives,” Russia’s Foreign Ministry said.

Iranian Deputy Foreign Minister Hossein Amir Abdullahian said the attack “demonstrates the shared goals of terrorists and the Zionist regime,” Fars reported.

An aide to Supreme Leader Ayatollah Ali Khamenei said Saturday that Iran would consider any attack on Syria as an attack on itself.

In Damascus, residents doubted Syria would fight back. One mother of five said she had heard retaliation would come later. “They always say that. They’ll retaliate, but later, not now. Always later,” she said, laughing.

“The last thing we need now is Israeli fighter jets to add to our daily routine. As if we don’t have enough noise and firing keeping us awake at night.”

Details of the strike remain sketchy and, in parts, contradictory. Syria said Israeli warplanes, flying low to avoid detection by radar, crossed into its airspace from Lebanon and struck the Jamraya military research center.

But diplomats and rebels said the jets hit a weapons convoy heading from Syria to Lebanon while the rebels said they, not Israel, attacked Jamraya with mortars.