(CNN) -- Shouting condemnation and promises of retaliation, Syria, Iran and Hezbollah on Thursday condemned Israel's decision to send warplanes into Syria, calling its airstrike a day before "inhuman" and "barbaric."
Russia also condemned Wednesday's attack, saying it would represent an unprovoked violation of United Nations charter if confirmed.
Syria's Foreign Ministry summoned the commander of U.N. forces in the Golan Heights on Thursday to formally complain about the incident, while Iran's deputy foreign minister, Hossein Amir Abdollahian, warned the attack would have "dire consequences" for Israel, according to Iran's semiofficial Mehr News Agency.
Just last week, Abdollahian warned that Iran would consider any attack on Syria as an attack on itself, Mehr reported at the time.
Meanwhile, a U.S. official said reports that Israel had struck a Syrian research facility were wrong, instead saying warplanes hit only one target: a convoy carrying surface-to-air missiles.
A source said Wednesday that Israeli fighter jets had struck a Syrian convoy suspected of moving Russian-made missile parts that could have been used to attack Israel. A senior U.S. official said the weapons were bound for the militant group Hezbollah in Lebanon. Syria and Iran back the group, which the United States has designated as a terrorist organization.
However, Syria's military said Wednesday and again Thursday in state-run media that Israel had struck at a defense research facility near the capital of Damascus, killing two workers and injuring five others.
The report in Syrian state media tied the attack to Syria's ongoing rebellion, saying Israel struck the site after repeated attempts by what the regime of Syrian President Bashar al-Assad refers to as terrorist groups failed to capture the facility.
Experts say al-Assad's regime is faltering after nearly two years of fending off the persistent rebellion, and a former high-ranking Israeli Intelligence official said Hezbollah probably wants to take hold of all the weapons it can before that happens. Providing Hezbollah with Syrian arms would better equip it to attack Israel, the official said.
In recent years, Syria has transferred to Hezbollah Scud missiles that can carry chemical weapons. U.S. authorities say they do not believe the strike was linked to growing concerns about Syria's chemical weapons, the senior U.S. official said Wednesday.
The attack was not particularly surprising, said senior Brookings Institution fellow Michael O'Hanlon.
"At first glance, it likely won't be seen as a large escalation, though there's still a possibility for retaliation."
State Department spokeswoman Victoria Nuland and White House spokesman Jay Carney declined to comment on the airstrike Wednesday. Carney referred questions to Israel, which also has been tight-lipped about the strike.
On Thursday, Syria took its case against Israel to Maj. Gen. Iqbal Singh Singha, the commander of the United Nations Disengagement Observer Force in the Golan Heights, former Syrian territory seized by Israel in 1967.
Foreign Ministry officials demanded a U.N. response to the incident, which it said violates the U.N. charter and the 1974 agreement between Syria and Israel negotiated after the Yom Kippur War.
U.N. Secretary-General Ban Ki-moon's office issued a statement Thursday expressing "grave concern" about the incident, but said U.N. officials lacked details about exactly what had happened.
Russia, a Syrian ally, said it also had "grave concern" about Wednesday's airstrike.
"If the information is confirmed, we are dealing with unprovoked attacks on targets situated on the territory of a sovereign state that grossly violates the U.N. Charter and is unacceptable whatever motives are used to justify it," the Russian Foreign Ministry said Thursday.
Iran also backed its close ally. The semiofficial Iranian Student News Agency quoted Foreign Minister Ali Akbar Salehi as saying the attack was "in line with the West's policies of undermining the victories of the Syrian government."
Syria's ambassador to Lebanon, Ali Abdul Karim, said Syria reserves the right to a "surprise retaliation" against Israel, according to Hezbollah's official website, Moqawama.
"I cannot predict this, and this depends on the relevant authorities to decide on appropriate retaliation and decide the manner and place," Moqawama quoted him as saying.
CNN's Saad Abedine contributed to this report.