Smoke billows over southern Lebanon following Israeli strikes, amid ongoing cross-border hostilities between Hezbollah and Israeli forces, as seen from Tyre, Lebanon, Sept. 23. Reuters-Yonhap

Israel attacked hundreds of Hezbollah targets on Monday in airstrikes which Lebanese health authorities said killed at least 100 people, making it the deadliest day in Lebanon in nearly a year of conflict.

After some of the heaviest cross-border exchanges of fire since the conflict flared, Israel warned people to evacuate areas where it said the armed group was storing weapons.

After almost a year of war against Hamas in Gaza on its southern border, Israel is shifting its focus to its northern border, from where Iran-backed Hezbollah has been firing rockets into Israel in support of its ally Hamas.

"The actions will continue until we achieve our goal to return the northern residents safely to their homes," Israeli Defense Minister Yoav Gallant said in a video published by his office, setting the stage for a long conflict as Hezbollah has vowed to fight on until there is a ceasefire in Gaza.

"These are days in which the Israeli public will have to show composure."

He was speaking after the Israeli military targeted Iran-backed Hezbollah in Lebanon's south, eastern Bekaa valley and northern region near Syria.

Lebanon's health ministry said at least 100 people had been killed, including women, children and medics, and more than 400 wounded in Israel's strikes on Monday.

Israeli army spokesperson Avichay Adraee said on X that more than 300 Hezbollah targets had been struck so far after earlier warning that airstrikes were imminent on houses in Lebanon where "Hezbollah hid weapons".

In response, Hezbollah said it had launched rockets at Israeli military posts.

Another round of attacks was expected. Israeli aircraft are preparing to attack Hezbollah strategic weapons stashed in houses in Lebanon's Bekaa valley, the Israeli military spokesperson said, calling on civilians to evacuate immediately.

"The sights now from south Lebanon are of secondary explosions of Hezbollah weapons, which are exploding inside houses. In every house we are attacking there are weapons. Rockets, missiles, unmanned aerial vehicles that were meant for and aimed at killing Israeli civilians," Rear Admiral Daniel Hagari said in a televised statement.

The airstrikes have intensified pressure on Hezbollah, which last week suffered an attack its Secretary General Hassan Nasrallah called "unprecedented in the history" of the group, after thousands of pagers and walkie-talkies used by its members exploded.

The operation was widely blamed on Israel, which has not confirmed or denied responsibility.

In another major blow, an Israeli airstrike on Beirut's southern suburb on Friday targeted senior Hezbollah commanders, killing 45 people, according to the Lebanese health ministry.

Hezbollah said 16 members of the group were among the dead, including senior leader Ibrahim Aqil and another commander, Ahmed Wahbi.

One person was slightly hurt by shrapnel from the latest rocket barrage at northern Israel, according to the Israeli ambulance service.

Imad Kreidieh, the head of Lebanese telecoms company Ogero, told Reuters on Monday that more than 80,000 automated calls asking people to evacuate their areas were detected on the network. Not all were answered. Such calls were "psychological warfare to make havoc and chaos," he added.

Evacuation calls have been received on phones as far as the Lebanese capital, Beirut.

An armed Israeli fighter jet is seen from Haifa, Israel, Sept. 23. AP-Yonhap

Psychological War

Lebanon's information minister Ziad Makary said his ministry had received a call ordering the building to evacuate, but said the ministry would do no such thing. "This is a psychological war," Makary told Reuters.

In the eastern Beirut district of Sassine, state employee Joseph Ghafary said he feared that Hezbollah would respond to Israel's intensified strikes and that a full-blown war would break out.

"If Hezbollah carries out a major operation, Israel will respond and destroy more than this. We can't bear it," he said.

"Israel wants to strike, it wants to keep going, meaning it is squeezing Sayyed Hassan (Nasrallah) to start a war. It is definitely dangerous."

Mohammed Sibai, a shop owner in the Beirut neighbourhood of Hamra, told Reuters that he saw the escalation in strikes as "the beginning of the war." "If they want war, what can we do? It was imposed on us. We cannot do anything," he said. Asked by reporters about a possible Israeli ground incursion into Lebanon, Hagari said earlier "we will do whatever is needed" in order to return evacuated residents of northern Israel to their homes safely, a war priority for the Israeli government.

Hagari presented in a media briefing an aerial video of what he described as Hezbollah operatives trying to launch cruise missiles from a civilian house in Lebanon, and the subsequent Israeli strike moments before it was launched.

"Hezbollah is endangering you. Endangering you and your families," Hagari said. (Reuters)