Diplomatic pressure mounted Monday to avert an escalation between Iran and Israel following high-profile killings that have sent regional tensions soaring, while numerous governments urged their citizens to leave Lebanon.
Israeli Prime Minister Benjamin Netanyahu said late Sunday that his country was "determined to stand against" Iran and its allied armed groups "on all fronts".
As its war against Iran-backed Hamas in Gaza nears its 11th month, Israel has been bracing for retaliation from the Tehran-aligned "Axis of Resistance" for the killing of two senior figures.
Palestinian armed group Hamas's political leader Ismail Haniyeh was killed in Tehran on Wednesday in an attack blamed on Israel, which has not directly commented on it.
The killing came hours after an Israeli strike on Beirut left Hezbollah military chief Fuad Shukr dead.
Tehran said on Monday that "no one has the right to doubt Iran's legal right to punish the Zionist regime" for Haniyeh's killing.
United States President Joe Biden, whose country has sent extra warships and fighter jets to the region in support of Israel, was to hold crisis talks on Monday with his national security team.
The head of the US military command covering the Middle East, General Michael Kurilla, arrived in Israel and met Israel's military chief Lieutenant-General Herzi Halevi for a security assessment, an Israeli military statement said.
US Secretary of State Antony Blinken told his counterparts from the G7 nations in a conference call on Sunday that any attack by Iran and Hezbollah could happen as early as Monday, US news site Axios reported.
Blinken asked his counterparts to place diplomatic pressure on Tehran, Hezbollah and Israel to "maintain maximum restraint", it added.
Government spokesman David Mencer said Israel is "preparing for any scenario both offensively and defensively".
In the northern port city of Haifa, shop owner Yehuda Levi, 45, told AFP that Israelis are used to conflict, but facing a multi-pronged attack "is a little tricky".
"It's difficult, but we believe we're a strong country. We're going to win this war."
'Path of dialogue'
Experts and diplomats fear that the expected attack on Israel could rapidly spiral into a regional war, in which Lebanon would be on the front line.
Turkey on Monday joined multiple nations calling on their citizens to leave Lebanon, where Hezbollah is based.
Numerous airlines have suspended flights to the country or limited them to daylight hours.
Germany's Lufthansa, which has already suspended flights to the region including Tel Aviv, said its planes would avoid Iraqi and Iranian airspace until at least Wednesday.
Royal Jordanian Airlines said it would be operating three flights this week to transport nationals out of Beirut.
The United Nations' rights chief Volker Turk called on "all parties, along with those states with influence, to act urgently to de-escalate what has become a very precarious situation".
Italian Foreign Minister Antonio Tajani, whose country currently holds the rotating G7 presidency, similarly appealed for "the parties involved to desist from any initiative that could hinder the path of dialogue and moderation".
French President Emmanuel Macron joined the chorus of countries calling for "restraint" in the Middle East, during conversations with the leaders of Saudi Arabia and the United Arab Emirates.
On Sunday, Jordan's Foreign Minister Ayman Safadi made a rare trip to the Iranian capital during which he delivered a message from King Abdullah II to President Masoud Pezeshkian.
Political analyst Oraib Rantawi said Jordanian "airspace will probably be a theatre for missiles and anti-missile" fire in any direct Iranian-Israeli clashes, but Amman would strongly object to violations of its sovereignty.
"The Iranians must find other ways to spare Jordan this embarrassment," Rantawi, director of the Amman-based Al Quds Center for Political Studies, told AFP.
The Israel-Hamas war in the Gaza Strip, triggered by the Palestinian group's October 7 attack on Israel, has already drawn in Iran-backed militants in Syria, Lebanon, Iraq and Yemen.
The Hamas attack resulted in the deaths of 1,197 people, mostly civilians, according to an AFP tally based on Israeli official figures.
Militants also seized 251 hostages, 111 of whom are still held captive in Gaza, including 39 the military says are dead.
In Tel Aviv on Monday thousands of Israelis gathered to mark the fifth birthday of child hostage Ariel Bibas, and to call for the liberation of him and his family.
Israel's retaliatory military campaign in Gaza has killed at least 39,623 people, according to the Hamas-run territory's health ministry, which does not give details of civilian and militant deaths.
Cross-border clashes
As the region braced for further escalation, Hezbollah and Israel kept up their near-daily exchanges of fire.
The Lebanese health ministry said three people were killed Monday in Israeli strikes on the country's south. Israel's military said it had struck militants operating a drone in the Mais al-Jabal area.
Hezbollah later said a fighter from that village had been killed.
Tehran has said it expects Hezbollah to hit deeper inside Israel and no longer be confined to military targets.
Far from the Lebanese border, the Israeli military said around 15 rockets had crossed from the southern Gaza Strip into Israel on Monday, with medics saying they were treating an injured man.
The war in Gaza has destroyed much of Gaza's housing and other infrastructure and uprooted most of the populated as malnutrition and disease spreads, according to the United Nations.
The main aid body in Gaza, the UN agency for Palestinian refugees, UNRWA, on Monday said nine of its employees, out of thousands it employs in the territory, "may have been involved" in the October 7 attack. They have been fired, a UN spokesman said.
Months of talks mediated by Qatar, Egypt and the United States aimed at a Gaza ceasefire and a hostage-release deal have repeatedly stalled, but diplomats say a Gaza truce would help to calm the wider region.