Israeli warplanes flew over Lebanon again on Friday, two days after air strikes targeted a convoy of arms or a weapons research base inside Syrian territory.

Andrea Tenenti, a spokesman for the UN forces in Lebanon, Unifil, confirmed that Israeli forces had continued to violate Lebanese airspace, but said this was routine. "On Tuesday [ahead of the air strikes] there were a high number of violations, but since then it has not been unusual," he told the Guardian.

Under UN security council resolution 1701, passed following the 2006 Israel-Lebanon war, Israeli planes are forbidden from flying over Lebanon.

Israel has maintained silence over Wednesday's bombing, despite a statement from the Syrian regime that a "scientific research centre" between Damascus and the Lebanese border had been hit. Reports described the centre as a large military complex with training and communications facilities. Western diplomatic and security sources said Israel's target was a convoy of trucks carrying Russian-made anti-aircraft missiles from Syria to the Hezbollah militia in Lebanon.

Shlomo Brom of Israel's Institute of National Security Studies said there was "no contradiction" between the two accounts. "The convoy may have been attacked while being loaded or while leaving the installation," he said. Hezbollah was keen to extract from Syria as much weaponry as possible before supply routes closed off.

Concern about possible retaliatory action was fuelled by comments made by an Iranian legislator. "Damascus retaliation against the illegal move of the Zionist regime is a right of the Syrian people," said Mohammad Hassan Asafari. If the Syrian regime failed to deliver a "proper response", Israel would not hesitate to carry out further attacks, he added.

The Israeli foreign ministry declined to comment on reports that its embassies and missions worldwide had been placed on a heightened security alert, and the Israeli Defence Forces declined to say whether leave had been cancelled for troops based in northern Israel and the Golan Heights.

Many Israeli analysts thought that the chances of immediate retaliation were low, with some suggesting that any response was more likely to be targeted at Israeli assets or citizens abroad rather than rocket attacks or other military action aimed at Israel itself.

"The combination of strategic circumstances in the region at the moment makes the chance of a direct Iranian response unlikely," wrote Amos Harel, Haaretz's defence correspondent. "A Syrian military response seems even less likely, though neither possibility can be ruled out. The most worrying unknown since Tuesday night concerns Hezbollah's reaction … Hezbollah is a sophisticated enemy operating in a tough environment. Complete restraint over the long term to Israel's actions could be considered weakness by Hezbollah, so we should expect some form of response, even if not immediately and not necessarily a broad rocket and missile attack on Israel."

Yedioth Ahronoth's defence analyst Alex Fishman wrote: "Something major went down in Syria, but a heavy smokescreen is already blurring the tracks … If the signal sent to the Syrians and to Hezbollah by whomever produced this show – telling them to stop the unmonitored circulation of the weapons held by the Syrian army – is not picked up, then the next operation will not be able to leave such a vague address. And this will bring the region into an open and violent clash.

"Missiles may not fly at Israel this time. It seems that this time, we will get through the storm safely. And the proof: the defence minister allowed himself to leave for a conference of defence ministers in Germany. But Israel should prepare for the possibility of acts of revenge overseas, in the style of the terror attacks that took place in the past."