Syria’s ambassador to Lebanon declared that Syria had “the option and the capacity to surprise in retaliation.” The Iranian deputy foreign minister warned that the attack would have “grave consequences for Tel Aviv,” while the Russian Foreign Ministry said the strike “blatantly violates the United Nations Charter and is unacceptable and unjustified, whatever its motives.” Lebanon’s Foreign Ministry also condemned the attack — as did some Syrian rebels, seeking to deny President Bashar al-Assad of Syria a chance to rally support as a victim of Israel.

Many questions swirled about the target, motivations and repercussions of the Israeli attack, which Arab and Israeli analysts said demonstrated the rapid changes in the region’s strategic picture as Mr. Assad’s government weakens — including the possibility that Hezbollah, Syria or both were moving arms to Lebanon, believing they would be more secure there than with Syria’s beleaguered military, which faces intense attacks by rebels on major weapons installations.

Image Denying reports, Syria said Israeli jets had hit a defense research facility in Jimraya. Credit... The New York Times

American officials said Israel hit a convoy before dawn on Wednesday that was ferrying sophisticated SA-17 antiaircraft missiles to Lebanon. The Syrians and their allies said the target was a research facility in the Damascus suburb of Jamraya.

It remained unclear Thursday whether there was one strike or two. Also unclear was the research outpost’s possible role in weapons production or storage for Syria or Hezbollah, the militant Lebanese Shiite organization that has long battled with Israel and plays a leading role in the Lebanese government.