JERUSALEM — The Israeli military said on Wednesday that it was taking defensive measures to safeguard the country, preparing for the possibility that Israel becomes the target of retaliation for a Western attack on Syria, and the government authorized the calling-up of a limited number of reservists.

Although Israeli officials said they believed that the probability that Syria would strike against Israel remained low, Israelis lined up to collect gas masks from distribution centers around the country and jammed the phone lines and the Web site of the Israel Postal Company, which distributes the protective kits.

Prime Minister Benjamin Netanyahu urged calm. After security consultations at the Defense Ministry headquarters in Tel Aviv, he said in a statement: “There is no reason to change daily routines. At the same time, we are prepared for any scenario.” He added that the military was “ready to defend against any threat and to respond strongly against any attempt to harm Israeli citizens.”

On Tuesday, Mr. Netanyahu said Israel was “not part of the civil war in Syria” but would respond to any attack “in strength.”