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Israel's foreign minister warned on Wednesday his country will act immediately if it discovers Islamic militants are raiding Syria's chemical or biological weapons stocks, while Israelis rushed to stock up on gas masks as the bellicose rhetoric swells.

Israeli political and security leaders have been watching the intensified bloodletting in neighboring Syria with mounting concern, afraid that Lebanon's Hezbollah and other militant groups could raid these arsenals should the central government in Damascus collapse. In recent days, Israeli political leaders have said they would be prepared to strike weapons depots to prevent this from happening.

Reflecting the fears, Israeli officials reported a run on gas masks in recent days. Demand has almost doubled in the past few days, to 4,200 requests on Tuesday from a years-old average of about 2,200, said Merav Lapidot, a spokeswoman for the Israeli postal service, which distributes the masks.

Foreign Minister Avigdor Lieberman told Israel Radio that the government would not tolerate seeing Syria's chemical weapons fall into militant hands as tensions rise along his country's northern border.

"For us, that's a casus belli, a red line," he said.

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    Israel's military chief Lt. Gen. Benny Gantz, however, counseled restraint on Tuesday, warning that an attack on Syrian chemical weapons depots could drag Israel into a broader war.

    At this point, Israel's assessment is that Syria retains control over these arsenals.

    On Monday, the Syrian regime threatened to unleash its chemical and biological weapons if it faces a foreign attack, a threat widely believed to be directed at Israel.