Jim Hollander/European Pressphoto Agency
In East Jerusalem, Israelis distributed gas masks on Wednesday as worries about security spread. More Photos »
JERUSALEM — Israeli warplanes carried out a strike deep inside Syrian territory on Wednesday, American officials reported, saying they believed the target was a convoy carrying sophisticated antiaircraft weaponry on the outskirts of Damascus that was intended for the Hezbollah Shiite militia in Lebanon.
The American officials, who spoke on the condition of anonymity, said Israel had notified the United States about the attack, which the Syrian government condemned as an act of “arrogance and aggression.” Israel’s move demonstrated its determination to ensure that Hezbollah — its arch foe in the north — is unable to take advantage of the chaos in Syria to bolster its arsenal significantly.
The predawn strike was the first time in more than five years that Israel’s air force had attacked a target in Syria. While there was no expectation that the beleaguered Assad government had an interest in retaliating, the strike raised concerns that the Syrian civil war had continued to spread beyond its border.
In a statement, the Syrian military denied that a convoy had been struck. It said the attack had hit a scientific research facility in the Damascus suburbs that was used to improve Syria’s defenses, and called the attack “a flagrant breach of Syrian sovereignty and airspace.”
Israeli officials would not confirm the airstrike, a common tactic here. But it came after days of intense security consultations with Prime Minister Benjamin Netanyahu regarding the possible movement of chemical and other weapons around Syria, and warnings that Jerusalem would take action to thwart any possible transfers to Hezbollah.
Thousands of Israelis have crowded gas-mask distribution centers over the last two days. On Sunday, Israel deployed its Iron Dome missile defense system in the north, near Haifa, which was heavily bombed during the 2006 war with Lebanon.
Syria and Israel are technically in a state of war but have long maintained an uneasy peace along their decades-old armistice line. Israel has mostly watched warily and tried to stay out of Syria’s raging civil war, fearful of provoking a wider confrontation with Iran and Hezbollah. In November, however, after several mortars fell on Israel’s side of the border, its tanks struck a Syrian artillery unit.
Several analysts said that despite the increased tensions, they thought the likelihood of retaliation for the airstrike was relatively low.
“It is necessary and correct to prepare for deterioration — that scenario exists,” Danny Yatom, a former chief of the Mossad, Israel’s intelligence agency, told Ynet, a news Web site. “But in my assessment, there will not be a reaction, because neither Hezbollah nor the Syrians have an interest in retaliating.”
Syria’s president, Bashar al-Assad, “is deep in his own troubles,” Mr. Yatom said, “and Hezbollah is making a great effort to assist him, in parallel with its efforts to obtain weapons, so they won’t want to broaden the circle of fighting.”
In the United States, the State Department and Defense Department would not comment on reports of the strike.
Russia, which has carried out a vigorous diplomatic battle to deter foreign military intervention in the Syrian conflict for more than a year, issued a statement of concern early on Thursday, describing the strikes as “an attack by Israel’s air force on objects in Syria, near Damascus.”
“If this information is confirmed, this is an unprovoked attack on the territory of a sovereign nation, which blatantly violates the U.N. charter and is unacceptable and unjustified whatever its motives,” said a statement posted on the web site of the Russian Foreign Ministry.
Moscow said it would take immediate steps to clarify what had happened, and reiterated its longstanding insistence on a political solution and “the unacceptability of any kind of external intervention.”
The episode illustrated how the escalating violence in Syria, which has already killed more than 60,000, is drawing in neighboring states and threatening to destabilize the region further.
Iran has firmly allied itself with Mr. Assad, sending personnel from its Islamic Revolutionary Guards Quds Force to Syria and ferrying military equipment to Syria through Iraqi airspace.
