Israel will not tolerate the transfer of advanced weapons to Hezbollah, Defence Minister Ehud Barak said on Sunday, as fears grew about the future of Syria's suspected chemical arsenal.

"The State of Israel cannot accept the transfer of advanced weapons systems from Syria to Lebanon," he said in remarks relayed by his office.

"We are closely monitoring the possibility that Hezbollah will try to take advantage of the opportunity to transfer advanced weapons systems," he said, referring to Lebanon's Shiite militia, a key ally of the embattled regime of Syrian President Bashar al-Assad.

"It is inappropriate to say any more than this -- when we would act, how we would act, if indeed we would act," he said in remarks communicated by a spokesman.

Israel has frequently raised the alarm over the possibility of Hezbollah gaining access to Syria's suspected stockpile of chemical and other advanced weapons, fearing that such a scenario could become reality in the chaos that would accompany a collapse of the Assad regime.

And on Friday, Barak said he had told the army to prepare for a possible military operation.

"We are monitoring the situation on the Syrian-Lebanese border, that during Assad's downfall, Hezbollah will try to put their hands on advanced anti-aircraft systems, surface-to-surface missiles or elements of chemical weapons, and transfer them to Lebanon," he told private Channel Two television.

"We are following these things and preparing. I've ordered the army to prepare in such a way that if situations arise that will force us to consider action, we will be able to consider it."

Asked about Barak's remarks, Prime Minister Benjamin Netanyahu ruled out the option of seizing any such weapons.

"We didn't consider seizing them," he said in an interview with Fox News Sunday. "There are other possibilities."

Netanyahu said that it was unimaginable that Hezbollah, which Israel blames for a recently deadly suicide bombing in Bulgaria that killed five Israelis and their local driver, get its hands on chemical weapons.

"I think someone will have to act... and the need might arise if there is a regime collapse, but not a regime change" in Syria, he said.

"We'll have to consider our action," he said, stressing that Israel did not "preclude" such an option.

On Wednesday, the New York Times reported that US defence officials had held talks with their Israeli counterparts over whether Israel might strike at Syria's weapons facilities as its regime faces possible collapse.

Damascus has been engulfed in clashes over the past week, with heavy fighting breaking out across several districts as the Assad's forces try to stamp out the more than 16-month uprising.

More than 19,000 people have been killed since the revolt erupted in March 2011, the Syrian Observatory for Human Rights said on Sunday.