Israel has implicitly confirmed it carried out an air strike in Syria, sparking a warning from Iran, but the Jewish state's next step in anticipation of a post-Bashar al-Assad era remains a mystery.

Defence Minister Ehud Barak told a defence conference in Munich on Sunday that an air raid last week that Syria said targeted a military complex near its capital was "another proof that when we say something we mean it."

He reiterated that Israel would not allow advanced weapon systems to fall into the hands of Lebanon's Shiite militant group Hezbollah, an ally of Damascus.

The minister stopped short of giving explicit confirmation of the air strike and there has still been no official comment from either the Israeli military or the government.

The New York Times, citing a senior US military official, reported Sunday that the air strike may have damaged Syria's main research centre on biological and chemical weapons.

Barak's comments came a day after US Defence Secretary Leon Panetta said Washington was increasingly concerned that "chaos" in Syria could allow Hezbollah to obtain sophisticated weapons from the Damascus regime.

"The chaos in Syria has obviously created an environment where the possibility of these weapons, you know, going across the border and falling into the hands of Hezbollah has become a greater concern," Panetta told AFP.

The Israeli raid on Wednesday targeted surface-to-air missiles and an adjacent military complex believed to house chemical agents, according to a US official who spoke on condition of anonymity. Syria has threatened to retaliate.

In a sign of increased border tensions, Israel has moved three of its Iron Dome missile defence batteries to its north, from where they can cover possible fire from Syria or Lebanon.

-- Israel will 'regret' --

Iran's security chief Saeed Jalili, on a visit to Damascus on Monday, implicitly warned that Israel would be made to regret its actions.

"Just like it regretted all its wars... the Zionist entity will regret its aggression against Syria," said Jalili, who heads Iran's Supreme National Security Council.

"The Muslim world supports Syria," Jalili said. "Syria is at the forefront of the Muslim world's confrontation" with Israel.

Ephraim Halevy, a former head of Mossad, the Israeli foreign intelligence agency, wrote Monday in top-selling daily Yediot Aharonot that his country had no intention of becoming embroiled in Syria's internal turmoil.

"Israel is not involved in the Syrian civil war or in the Iranian warfare on Syrian soil," he wrote.

"From all standpoints, it would have preferred that this conflict had not broken out in the first place, and for Israel to continue to enjoy the absolute quiet along the armistice lines drawn between the two states following the (1973) Yom Kippur War."

"This is the reason that it has displayed restraint both in its actions and in its dearth of official statements," Halevy added.

The raid "shows how the new security situation in Israel is complex and complicated," military analyst Avi Issacharof wrote on the news site Walla. "This new year will be decisive for Israel, not only in the context of the Iranian nuclear programme."

Israeli leaders fear a possible transfer of Syrian chemical and biological weapons to Hezbollah, but also that a general destabilisation of the country could turn it into a preserve of radical Islamist groups.

"A number of ideologically radical groups affiliated with Al-Qaeda have infiltrated the governmental vacuum (in Syria) that contributes to the chaos," said Issacharof.

Israeli leaders, particularly Barak, have repeatedly predicted President Assad's imminent fall and the military is planning its response.

Israel plans to declare a buffer zone inside Syria border to prevent radical groups from getting too close to its territory when the embattled Damascus regime topples, security sources told AFP on Sunday.