Prime Minister Benjamin Netanyahu on Thursday said Israel deployed its Iron Dome missile defence system to bolster its security as the West weighed military strikes on neighbouring Syria.
But he echoed President Shimon Peres in insisting that Israel is not involved in Syria's civil war but will respond with all its might if attacked.
"We have decided to deploy Iron Dome and other interceptors," Netanyahu said, in a statement released by his office, ahead of holding security talks at the defence ministry.
"We are not involved in the war in Syria. But I repeat: if anyone tries to harm Israeli citizens, Tsahal (the Israeli army) will respond with force," Netanyahu said in other remarks broadcast by Israeli television.
His comments come as Britain and the United States laid out their case for punitive strikes on Syria over an alleged chemical attack last week that rights groups say killed hundreds.
Earlier Peres said Israel will hit back if its security is at stake.
"Israel was not, and is not, involved in the Syrian fighting but if anyone tries to harm us we will respond with all our might," Peres was quoted as saying in a statement from his office.
"Israel has a strong army, modern and powerful, and a more advanced defence system than ever before," he added.
Army chief of staff Lieutenant General Benny Gantz said his forces were "ready for all scenarios," but added: "I hope we will not have to send them into action."
Peres said the situation in Syria, where a civil war that erupted in March 2011 has killed more than 100,000 people, "is not a local incident but a crime against humanity."
Israeli media and officials sought to calm the public on Thursday, as queues for gas masks lengthened.
There are fears that it the United States and its allies launch military strikes on Syria, forces of Syrian President Bashar al-Assad could retaliate against Israel, Washington's key ally in the region.
"Keep calm and carry on" was the title of a front-page analysis in the Jerusalem Post, echoing a slogan designed by the British government in World War II.
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"With (Israeli) military intelligence keeping more eyes and ears open to enemy activity than ever before, the combination of Israel's firepower and accurate intelligence would spell very bad news for the Assad regime should it choose to target Israel in response to an attack on Syria by the United States," the Post wrote.
"Doing so would likely sign his regime's death certificate."
On Wednesday, Netanyahu's security cabinet authorised a limited call-up of reservists, but the premier said members of the public had "no reason to change their routines."
Haaretz daily said those to be called up numbered "a few hundred" personnel considered vital, including members of missile defence, air force, intelligence and civil defence units.
"We need to make preparations but also to go about our daily lives," Defence Minister Moshe Yaalon said on Wednesday.
News website Ynet reported on Thursday that "hundreds" of people were waiting outside a gas mask distribution centre in central Tel Aviv before it opened, and public radio said "thousands" were queueing at a distribution site in the northern city of Haifa.
Maariv said a centre in Jerusalem was forced to close on Wednesday after anxious residents grabbed all the mask kits on the premises.
Nevertheless, Maariv reported, "security officials said that the situation assessment was that the likelihood of an attack on Israel was low."
The kits were first distributed during the 1991 Gulf War over Kuwait when Saddam Hussein's Iraq fired Scud missiles at Israel as the US-led coalition launched Operation Desert Storm.
The kits also contain syringes of the anti-nerve gas agent atropine for self-injection.
Yediot Aharonot diplomatic writer Shimon Shiffer recalled the 1991 attacks, which did not deliver non-conventional warheads and caused few casualties.
"Yesterday, against the backdrop of pictures of panicked civilians crowding the distribution centres for gas mask kits, I remembered something I said back then: 'There are no chemical weapons, and there will be no chemical weapon attack,'" Shiffer wrote in the top-selling daily.
"It seems to me that what was correct then, is correct today too. I dare to say that no chemical weapon attack is expected on Israeli targets. We can relax."