Russia has expressed concern at an alleged Israeli attack on Syria, saying such a strike would be an unacceptable violation of the UN Charter.
Syria's army said Israeli jets had targeted a military research centre north-west of Damascus on Wednesday, killing two people and wounding five.
It denied reports that lorries carrying weapons bound for Lebanon were hit.
A Syrian official and Iranian deputy minister have suggested there could be retaliation.
The Syrian army statement about the incident, carried on state media, said Israeli fighter jets had carried out a direct strike on a scientific research centre in Jamraya.
The Russian Foreign Ministry said: "If this information is confirmed, then we are dealing with unprovoked attacks on targets on the territory of a sovereign country, which blatantly violates the UN Charter and is unacceptable, no matter the motives to justify it."
Relations between Russia and Israel have been improving in recent years as trade and economic ties have grown stronger, says the BBC's Steve Rosenberg in Moscow.
But Moscow is a close ally of President Assad, which would explain its concern at the reports, our correspondent adds.
It has steadfastly refused to denounce Syrian President Bashar al-Assad during the 22-month conflict that has killed more than 60,000 people.
Missiles heading for border?
The attack came as Israel voiced fears that Syrian missiles and chemical weapons could fall into the hands of militants such as the Lebanese Shia militant group Hezbollah.
Israel and the US have declined to comment on the reported incident.
Any Israeli attack on Syria could cause a major diplomatic incident, analysts say, as Iran has said it will treat any Israeli attack on its ally Syria as an attack on itself.
Iran's foreign minister condemned the alleged air strike as an "overt assault based on the West's policy" to undermine stability in Syria.
"The Zionists got ahead of themselves in trying to cover up the successes of the Syrian government and nation in maintaining the existing government and restoring stability and security," Ali Akbar Salehi was quoted as saying by the semi-official ISNA news agency.
Iran's Fars news agency quoted the Deputy Foreign Minister Hossein Amir Abdollahian as saying the raid would have "grave consequences for [the major Israeli city of] Tel Aviv".
Syrian Ambassador to Lebanon Ali Abdul-Karim Ali said Damascus could take a "surprise" decision to retaliate.
Lebanese security sources, Western diplomats and Syrian rebels say an arms convoy near Lebanon's border was targeted. The Associated Press quoted a US official as saying the lorries were carrying Russian-made SA-17 anti-aircraft missiles.
The Lebanese military and internal security forces have not confirmed the reports, but say there has been increased activity by Israeli warplanes over Lebanon in the past week, and particularly on Tuesday and the early hours of Wednesday morning.
Correspondents say Israel fears Hezbollah could obtain anti-tank and anti-aircraft missiles, thus strengthening its ability to respond to Israeli air strikes.
Israel believes Syria received a battery of SA-17s from Russia after an alleged Israeli air strike in 2007 that destroyed a Syrian nuclear reactor near Deir Ezzor in eastern Syria, analysts say.
The US government said in 2008 that the reactor was "not intended for peaceful purposes".
Hezbollah said Wednesday's target was the Jamraya centre, condemning the attack as "an attempt to thwart Arab military capabilities" and pledging to stand by its ally Mr Assad.
Iron Dome move
BBC Middle East correspondent Wyre Davies says that while none of the reports can be verified, some well-placed diplomats and military sources say they would not be surprised if Israel had acted, given the recent instability in Syria.
The Syrian army statement said the Jamraya centre - which was focused on "raising our level of resistance and self-defence" - was damaged in the attack, and specifically denied reports that an arms convoy had been hit.
It said "armed terrorist gangs" - a term the government uses to describe rebel groups - had tried and failed repeatedly to capture the same facility in recent months.
Some reports suggest the facility could be Syria's Scientific Studies and Research Centre, believed to be the state organisation responsible for developing biological and chemical weapons.
The reported attack came days after Israel moved its Iron Dome defence system to the north of the country.
Israel has also joined the US in expressing concern that Syria's presumed chemical weapons stockpile could be taken over by militant groups.