Israeli forces attacked a target on the Syrian-Lebanese border overnight, Western diplomats and regional security sources said on Wednesday, at a time of growing concern over the fate of Syrian chemical and conventional weapons.

The Israel Defense Forces refused to confirm or deny the report. "We do not comment on reports of this kind," an IDF spokeswoman said.

The reported attack came soon after the Lebanese media said that Israel Air Force jets had flown over Lebanon's airspace in three separate missions late Tuesday and early Wednesday. There was no confirmation of that report from Israel, either.

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11:55 P.M. Syrian news website Al Hakika reports that the information on military facility was given to Israeli and American agents by rebel forces after receiving it from a senior official who worked there. The official, the report said, was arrested some ten months ago.

The site is located about five kilometers from Bashar Assad's palace and is secured by the president's guard. Until recently, anti-aircraft missiles were stationed there, but went out of commission due to the intense fighting in the area.

Al Hakika also claims that Israel tried to recruit agents working in the facility in order to shed light on its activity, mainly the development of chemical and biological weapons. 

11:45 P.M. Diplomatic sources from three countries told Reuters that chemical weapons were believed to be stored at Jamraya, and that it was possible that the convoy was near the large site when it came under attack. However, there was no suggestion that the vehicles themselves had been carrying chemical weapons.

Several rebel sources, however, including a commander in the Damascus area, accused the authorities of lying and said the only attacks at Jamraya had been mortar attacks by insurgents. "This episode boils down to a warning by Israel to Syria and Hezbollah not to engage in the transfer of sensitive weapons," the source said. "Assad knows his survival depends on his military capabilities and he would not want those capabilities neutralized by Israel - so the message is this kind of transfer is simply not worth it, neither for him nor Hezbollah." (Reuters)

10:00 P.M. Sky News in Arabic reports that Syrian opposition activists claim that the research institute that was attacked is known to be a weapons development center, which also produces chemical weapons.

9:20 P.M. Syrian state TV and army spokesmen say that Israeli warplanes bombed a military research center in the Jamraya area northwest of the capital, Damascus, killing two people, wounding five and causing severe damage to the facility. According to the report, Israeli fighter jets infiltrated Syrian airspace from the southwest, flying under the radar at low altitude. Army figures called the strike a serious violation of Syrian sovereignty and asserted that Israel was trying to aid anti-Assad rebels. They did not mention any Syrian response to the attack.

8:30 P.M. White House Press Secretary Jay Carney, asked during his daily press conference about reports of an Israeli attack in Syria, responded: "No comment. I refer you to the Israeli government." (Barak Ravid)

7:05 P.M. Speaking to the Associated Press on condition of anonymity, a U.S.­ government official confirms that the Israeli strike hit a convoy of trucks. U.S. officials, however, say they are tracking Syria's chemical weapons and that they still appear to be solidly under regime control. Israel suspects that Damascus obtained a battery of SA-17s from Russia after an alleged Israeli airstrike in 2007 that destroyed an unfinished Syrian nuclear reactor. The Israeli military declined to comment, and Syrian officials and state media continue to be silent on the issue. (AP)

6:48 P.M. The website Lebanon Now reports that the convoy that was attacked departed from somewhere around the city of al-Kassir in western Syria, located some 15 kilometers from the Lebanese border, and was headed for the Hermel area in northern Lebanon.  The source added that the convoy was carrying self-propelled strategic weapons meant for Hezbollah. (Jacky Khoury)

6:10 P.M. Speaking to the Associated Press, two "regional security officials" say Israel conducted an air strike inside Syria overnight near the border with Lebanon. While they did not say what the target was, they did say that Israel had been making plans in the days leading up to the air strike to hit a shipment of weapons bound for the anti-Israel militant group Hezbollah in Lebanon. According to the officials, the shipment included sophisticated, Russian-made SA-17 anti-aircraft missiles, which would be strategically "game-changing" in the hands of Hezbollah. (AP)

5:40 P.M. Al-Arabiya reports that the target of the air strike was a convoy of trucks carrying advanced anti-aircraft missiles. Sky News correspondent Sam Kiley, quoting security sources not connected to the attack, also reported that the attack was carried out against trucks carrying anti-aircraft missiles capable of limiting the freedom of action of Israeli Air Force jets over Lebanon. Kiley also suggested that the missiles could be of the type used against naval ships.

4:11 P.M. Lebanese security official says no evidence found of Israeli strikes on Lebanon's side of the border. (Haaretz)

4:07 P.M. A few hours after first reports, both Al-Jazeera and Al Arabiya are still ignoring the incident. (Haaretz)

4:02 P.M. Sky News Foreign Affairs Editor Tim Marshall: "If you put it all together and if there is movement of significant weapons coming out of Syria toward Lebanon, it would be probably be one of two things: Chemical weapons, or equally problematical for the Israelis, the air defense systems that Syria has many of. Both of those are a red line for the Israelis."

3:57 P.M. Minister Silvan Shalom: "The international community has stated more than once that it takes developments in Syria, which might have negative ramifications, very seriously. Any negative development, of course, should be prevented." (Army Radio)

3:23 P.M. Military Intelligence chief Aviv Kochavi and National Security Adviser Yaakov Amidror return from consultations in Washington and Moscow. (Barak Ravid)

3:20 P.M. Vice Premier Silvan Shalom, speaking on Israel Radio, was asked if there was unusual activity on the northern front. "The entire world has said more than once that it takes developments in Syria very seriously, developments which can begin negative directions. And therefore the world, led by [U.S.] President [Barack] Obama who has said this more than once, is taking all possibilities into account and of course any development which is a development in a negative direction would be something that needs stopping and prevention."

3:08 P.M. Lebanese news site Naharnet: Total of 12 Israeli fighter jets enter Lebanese air space over last 24 hours.

3:03 P.M. Security source tells AFP: The air force bombed a weapons convoy just as it was crossing from Syria into Lebanon.

2:56 P.M. The French newspaper Le Figaro: Israeli security sources say the target of the attack was a weapons convoy traveling from Syria into Lebanon. Not clear whether the attack took place inside Syria or in Lebanese territory.

2:27 P.M. Reuters reports that Israel has sent its national security adviser, Yaakov Amidror, to Russia and its military intelligence chief Major-General Aviv Kochavi to the United States for consultations.

1:58 P.M. Laura Rozen, of Al-Monitor, posts on Twitter that the "#Israel jets said to have struck alleged weapons convoy in Syria, after #IDF intel chief consultations in Washington".

1:45 P.M. Security source: There was definitely a hit in the border area";  A Western diplomat in the region who asked about the strike said "something has happened", without elaborating.

An activist in Syria who works with a network of opposition groups around the country said that she had heard of a strike in southern Syria from her colleagues but could not confirm. 

The sources, who declined to be named because of the sensitivity of the issue, had no further information about what might have been hit or where precisely the attack happened. 

Background

Earlier this week, the Lebanon Army reported that the IAF had violated Lebanon's airspace on Saturday in four different incidents. The Lebanese newspaper The Daily Star reported that IAF fighter jets were seen flying around the Beka'a Valley.

Also Saturday, the Lebanese daily Al-Mustaqbal said that an explosion struck a weapons storage facility in an area of southern Lebanon controlled by Hezbollah. The report was not confirmed by Lebanon's government or by the Lebanese army. The latter said it had conducted a number of controlled explosions on Saturday of munitions left over from the Second Lebanon War.

According to the daily, the explosion took place in the small town of Machghara, located in the Beka'a Valley. It said that a cloud of smoke was seen rising from the site, which was quickly cordoned off by Hezbollah forces.

On Sunday, Prime Minister Benjamin Netanyahu warned his cabinet ministers of the risk that chemical weapons from Syria could be falling into the hands of Hezbollah in Lebanon.

"It is necessary to look at our surroundings, both at what is happening with Iran and its proxies, and what is happening in other arenas - lethal weaponry in Syria, which is steadily breaking up," Netanyahu said during the weekly cabinet meeting in Jerusalem.

Also Sunday, Vice Premier Silvan Shalom said that any sign that Syria's grip on its chemical weapons was slipping, as President Bashar al-Assad fights rebels trying to overthrow him, could trigger Israeli intervention.

The commander of the Israel Air Force, Major General Amir Eshel, on Tuesday issued his own warning over the volatility of Syria and its weapons. Addressing the international space conference in Herzliya, Eshel described Syria as a "country falling apart", adding: "Nobody has any idea right now what is going to happen in Syria on the day after, and how the country is going to look. This [sectarian crisis] is happening in a place with a huge weapons arsenal, some of which are new and advanced, and some of which are not conventional."

Israeli sources said on Tuesday that Syria's advanced conventional weapons would represent as much of a threat to Israel as its chemical arms should they fall into the hands of Syrian rebel forces or Hezbollah guerrillas based in Lebanon.