Israel on Thursday wound up nationwide testing of an SMS warning system against missile attack, sending texts to mobile phones in Jerusalem and other parts of the country, a military spokeswoman said.
The five-day exercise, which began on Sunday, took place to the backdrop of mounting speculation over a possible Israeli strike on Iran's nuclear facilities and a resulting Iranian counter-attack.
The army said that along with Jerusalem, Thursday's test would include the Negev desert town of Arad, the northern cities of Afula and Hadera, and Upper Nazareth, a Jewish satellite of the Israeli Arab city.
A spokeswoman said that Nazareth itself, the largest Arab city in Israel, would not be included in the test but could not immediately say why.
The army says the warning messages are being sent in Hebrew, Arabic, English and Russian.
They are meant to warn of an imminent missile attack by Iran or Lebanon's Hezbollah militia, which could become a reality if Israel decides to mount a military strike on nuclear facilities in Iran.
Israel believes the Islamic republic is trying to develop a military nuclear capability under the guise of its civilian programme which it says would pose an existential threat to the Jewish state.
Opponents of an Israeli attack said on Thursday that around 500 academics and retired military personnel had signed a petition calling on air force pilots to refuse to carry out a unilateral strike.
"I understand the far-reaching implications of this petition," a statement quoted one of the signatories, Tel Aviv University law professor Menachem Mautner, as saying.
"The possibility of a decision to attack Iran has been keeping me awake for weeks."
The statement warns that injury to Iranian civilians as a result of radioactive leakage from any of the targeted facilities could expose pilots to future war crimes charges.
"We issue this appeal to you out of a deep sense of concern and anxiety," the petition tells the airmen. "Our fate, our very future lies very much in your hands."