"I would like to refer tonight to the various reports and rumours that we are on alert for the enemy's response to the territory of the State of Israel," military spokesman Rear Admiral Daniel Hagari said in an online briefing to journalists.

"I emphasise that as of now there is no change in the Home Front Command's defence policy," he said of a branch of the army that deals with the protection of civilians in times of war and emergency, including natural disasters.

Hagari and other top Israeli military and government officials, including Prime Minister Benjamin Netanyahu, have repeatedly said the country is prepared for any attack.

But Hagari said that Israel's protection is not "hermetic".

"We strive to give you the necessary warning to prepare for any threat," he said.

"The protection is not hermetic. Therefore, every citizen is required to know what the instructions are, wherever he is and to be vigilant."

Hagari also announced that the Home Front Command has launched a new system to alert citizens in the event of any emergency.

"The alert will be sent to mobile phones in the area under threat," he said.

"This is done without the need for an application and without any action on the part of the citizen."

Fears that the almost 10-month-old Gaza war could become a regional conflict after the killings Tuesday of Hezbollah top commander Fuad Shukr in a Beirut suburb and Hamas political chief Ismail Haniyeh the following day in Tehran.

Iran and its Lebanese ally Hezbollah have vowed to avenge the deaths which they blame on Israel.

Israel has claimed responsibility for killing Shukr but remained silent on Haniyeh's death.

Hezbollah has been trading near-daily cross-border fire with Israel since war erupted in Gaza on October 7 following Hamas's unprecedented attack on Israel.