Israel was preparing a military response to Iran's missile attack this week that heightened fears of a wider regional war, an Israeli official said Saturday, as fighting raged in Lebanon and in Gaza.
In its second-ever direct attack on its regional foe, the Islamic republic which backs armed groups across the Middle East on Tuesday launched about 200 missiles at Israel in revenge for a spate of Israeli killings of militant leaders.
The missile attack, which killed one person in the Israeli-occupied West Bank, caused some damage to an Israeli air base according to satellite images.
It came on the day Israeli ground forces began raids into Lebanon after days of intense strikes on Hezbollah strongholds across Lebanon, transforming nearly a year of cross-border exchanges with the Iran-backed militants into full-blown war.
A high-level Hezbollah source said Saturday that the group had lost contact with Hashem Safieddine, widely tipped to be the next Hezbollah leader, after air strikes this week in Beirut.
A second source close to the group also said communication had been cut off.
The movement has not yet named a new chief after Israel assassinated Hassan Nasrallah late last month in a massive strike in the Lebanese capital, triggering in part Iran's missile attack.
The Israeli military official, speaking to AFP on condition of anonymity as he was not authorised to discuss the issue publicly, said the army "is preparing a response to the unprecedented and unlawful Iranian attack."
He did not elaborate on the nature or timing of the response, which analysts and Israeli media said would likely be designed to deal an immense blow to Iran, despite international calls for de-escalation and warnings from Tehran it would retaliate.
Sina Toossi, a senior fellow at the Center for International Policy in Washington, told AFP that both Israel and Iran were "taking huge gambles".
"Everything right now hinges on Israel's response," he said.
Rapidly escalating violence this week also included intensifying Hezbollah rocket fire and strikes on Israel claimed by allies of Iran from as far away as Yemen, just before the first anniversary of Hamas's October 7 unprecedented attack on Israel which triggered war in Gaza.
Nearly a year into the Gaza war, Israel shifted its focus north, saying it aims to allow tens of thousands of Israelis displaced by Hezbollah attacks to return home.
Hezbollah said Saturday its fighters were confronting Israeli troops in Lebanon's southern border region, where the Israeli military said it struck militants inside a mosque in Bint Jbeil, a focus of this week's fighting.
The Israeli military said its forces were engaged in "limited, localized" raids in southern Lebanon, though the scale of their operations was not immediately clear.
The army reported frequent rocket fire from Lebanon, some of which was intercepted by air defences, as Hezbollah claimed a rocket attack on northern Israel's Ramat David air base, about 45 kilometres from the frontier.
The Lebanese group also said it fired rockets at a "military industries company" near Israel's coastal city of Acre.
In the first reported Israeli air strike on the northern Tripoli region in the current escalation, Hamas said "Zionist bombardment" of the Beddawi refugee camp killed one of its commanders, Saeed Attallah Ali, as well as his wife and two daughters on Saturday.
In downtown Beirut, Ibrahim Nazzal, who is among hundreds of thousands displaced by the violence, said: "We want the war to stop... all our homes are gone."
Across Lebanon, an intensified wave of strikes on Hezbollah strongholds killed more than 1,110 people since September 23, according to the health ministry.
The state-run National News Agency said that about a dozen strikes hit the Lebanese capital's southern suburbs overnight, with a fresh raid on Saturday around mid-day. It also reported more Israeli strikes in Lebanon's south and east.
In Hezbollah's south Beirut bastion, an AFP photographer saw some buildings reduced to rubble and fire raging in another.
Arriving in Lebanon, the head of the UN's refugee agency, Filippo Grandi, said "Lebanon faces a terrible crisis" and warned "hundreds of thousands of people are left destitute or displaced by Israeli air strikes".
Israel's recent attacks on Lebanon have killed an Iranian general, a host of Hezbollah commanders and, in the biggest blow to the group in decades, Nasrallah.
Iran's supreme leader Ayatollah Ali Khamenei, delivering a rare public sermon on Friday, said that "the resistance in the region will not back down with these martyrdoms."
Israeli bombardment has also put at least four hospitals in Lebanon out of service, the facilities said.
The UN peacekeeping force in Lebanon urged commitment "in actions, not just words" to Security Council Resolution 1701, which ended a 2006 war between Israel and Hezbollah and stipulated that only the Lebanese army and peacekeepers should be deployed in south Lebanon.
Iran's Foreign Minister Abbas Araghchi, visiting Damascus on Saturday after a stop in Beirut, renewed his call for ceasefires in both Gaza and Lebanon.
President Joe Biden said the United States, Israel's top military supplier, was working to "rally the rest of the world" to prevent the fighting from spreading even further.
US, Qatari, and Egyptian mediators tried unsuccessfully for months to reach a Gaza truce and secure the release of 97 hostages still held in the Hamas-ruled territory.
Medics and rescuers said Israeli fire early Saturday killed at least 12 people across Gaza.
The October 7 attack resulted in the deaths of 1,205 people, mostly civilians, according to an AFP tally based on Israeli official figures that include hostages killed in captivity.
Israel's retaliatory military offensive has killed at least 41,825 people in Gaza, the majority of them civilians, according to figures provided by the territory's health ministry and described as reliable by the UN.
For the first time in weeks, Israel told Palestinians to evacuate an area in central Gaza warning that troops were preparing to use "great force" against Hamas fighters around the strategic Netzarim Corridor.