An Israeli soldier drives an armored personal carrier during a military exercise in the Israeli controlled Golan Heights, near the border with Syria, Tuesday, May 7, 2013. (Ariel Schalit/AP)

The weekend airstrikes near the Syrian capital reportedly carried out by Israel have heightened concerns about terrorist attacks on Israeli tourists and other civilian targets in the coming weeks, U.S. officials and experts say, as Damascus and its allies vow to respond to what Syria has called an “act of war.”

On Tuesday, Syrian President Bashar al-Assad denounced Israel and said his nation was strong enough to stand up to its southern neighbor. The comments were Assad’s first since the airstrikes and came after a meeting with Iranian Foreign Minister Ali Akbar Salehi, who was visiting Damascus. Assad did not threaten retaliation, but he said Syria is “capable of facing Israel’s ventures.”

Although Israel has refused to comment on the strikes, U.S. officials said the attacks were aimed at a cache of advanced Iranian-built missiles apparently intended for Hezbollah, a Lebanese militant group closely allied with Assad.

U.S. and Middle Eastern officials say any retaliation would probably come in a familiar form: attempted attacks by Hezbollah operatives on Israeli or Jewish civilian targets, perhaps far outside the Middle East.

But they also said that the rigors of the ongoing civil war in Syria and Iran’s negotiations over its nuclear program could serve as restraints. The officials, who spoke on the condition of anonymity to provide intelligence assessments, said a terrorist attack would almost certainly be seen as preferable to a direct assault, which would risk an escalating conflict with Israel.

Hezbollah, a longtime foe of Israel with a vast international network and the patronage of Iran, has long been linked to assassinations and terrorist bombings on foreign soil, including a suicide attack last year on a bus filled with Israeli tourists in the Bulgarian resort city of Burgas.

“I expect more of the ‘shadow war’ we’re already seeing — soft targets, tourists — and targeting senior current or former Israeli officials,” said Matthew Levitt, a Hezbollah expert and former counterterrorism adviser and analyst at the Treasury Department and the FBI. “It’s already happening, and it will happen even more.”

Few options for Assad

The Israeli government has not publicly asserted responsibility for the airstrikes that occurred Friday and early Sunday, but senior officials privately confirmed that the targets were a shipment of Iranian-made surface-to-surface missiles intended for Hezbollah. Although Israel insists that its fight is not against Assad or the rebels fighting his regime but against Hezbollah , Syrian opposition groups say the airstrikes killed dozens of elite Syrian troops stationed nearby.

State-controlled news media reports in Syria continued to denounce the airstrikes as acts of war. One prominent newspaper, al-
Watan, reported that Assad had authorized terrorist operations inside Israel by Syrian-backed Palestinian militants. A report on Syria’s semiofficial al-Ikhbariya television network said Syrian military officials were preparing rocket strikes against Israel in the event of an escalation.

Despite the bluster, there has been no violence other than occasional stray mortar shells from Syria exploding harmlessly in the ­Israeli-occupied Golan Heights.

U.S. officials said Assad has few palatable options for retaliation after two years of conflict at home, which has left his military depleted as it struggles with a patchwork of rebel fighters who control large swaths of the country.

Assad’s inability to respond to the airstrikes — which, if Israel’s role is confirmed, would be the second and third Israeli attacks on Syrian targets this year — is a personal humiliation for the Syrian leader, even as it offers a chance to sway the opinions of some Arabs in his favor, said David Schenker, a former senior adviser to the Pentagon on Middle East policy and military affairs.

“Syria almost welcomes Israel’s involvement because it muddies the water,” Schenker said. “But it’s also embarrassing, because the state can’t do anything about it.”

Restraints on Iran

Assad’s key Shiite allies, Hezbollah and Iran, have denounced the airstrikes. Iran demanded a formal response from the United Nations, criticizing the attacks in a letter as “blatant acts of aggression” and a “serious violation of international law.” But several current and former U.S. officials said Iran wants to avoid direct hostilities amid sensitive international negotiations over its nuclear program and upcoming domestic elections.

Iran would probably pressure Hezbollah to show restraint as well, preferring to reserve the group’s stockpile of Iranian-made missiles and rockets as an insurance policy against a future Israeli strike on Tehran’s nuclear facilities, said Clifford Kupchan, a Middle East expert and former State Department official.

“Iran has been careful not to get itself bombed by the United States,” Kupchan said, “and it perceives Hezbollah as its key card in the event that Israel or the United States should ever attack its nuclear facilities.”

Despite its reported arsenal of about 60,000 missiles and rockets, Hezbollah has largely avoided military clashes with Israel since their last major conflict in southern Lebanon in 2006. Instead, it has engaged in covert attempts to kill Israeli and Western diplomats, businessmen and tourists over the past two years, in settings ranging from Bangkok to Istanbul to Washington.

This week, a judge in Kenya sentenced two Iranian nationals to life imprisonment for their role in a foiled scheme to blow up Kenyan hotels and businesses popular with Israeli and Western tourists.

Syrian Deputy Foreign Minister Faisal al-Mekdad appeared to be alluding to such attacks when he vowed in a televised interview that Syria would respond to the latest airstrikes in a manner and time of its choosing. “We have dealt with this on several occasions, and we retaliated in the way we wanted,” Mekdad told CNN on Sunday. “The retaliation was always painful.”