Israel launched air strikes into Lebanon on Sunday, saying it destroyed "thousands" of Hezbollah rocket launchers and thwarted a major attack, while the Lebanese group insisted it had been able to deliver a drone and rocket barrage of its own.
The result was perhaps the biggest exchange of fire in 10 months of a war which began with a Hamas attack launched from Gaza and has triggered both new violence on the Lebanon-Israel border and fears of a broader conflagration in the Middle East.
The Israeli military said around 100 of its fighter jets had struck more than 270 targets, "90 per cent" of which "were short-range rockets aimed at northern Israel".
Hezbollah, the powerful Iran-backed Lebanese armed group, denied that thousands of launchers had been destroyed or that Israel had thwarted a larger attack. It said its own operation "was completed and accomplished".
Israeli Prime Minister Benjamin Netanyahu told his cabinet the strikes were "not the final word" in the campaign against Hezbollah.
A soldier in the Israeli navy was killed in combat and two more wounded, the military said, with an official telling AFP their boat may have been hit by one of their own side's air-defence interceptors.
Hezbollah has traded near-daily cross-border fire with Israeli forces throughout the Gaza war, in what Hezbollah says is support for its Palestinian ally Hamas.
But fears of a wider regional conflagration soared after attacks in late July, blamed on Israel, killed Iran-aligned militant leaders including the Hamas political chief and a top Hezbollah commander, Fuad Shukr, which prompted vows of revenge.
Britain and Jordan were among those to appeal on Sunday for an end to the escalation and a ceasefire in Gaza.
Jordanian Foreign Minister Ayman Safadi also called for the UN Security Council to take "deterrent" and "effective" measures against Netanyahu and his ministers who "kill all chances of achieving peace".
Homes damaged
Hezbollah said its militants launched "a large number of drones" and "more than 320" Katyusha rockets targeting "enemy positions" across the border.
The group's leader Hassan Nasrallah named the "main target" as the Glilot military intelligence base near Tel Aviv, which Israeli media reported is home to the headquarters of the Mossad spy agency.
Israel's military said there were "no hits" on the base.
A secondary target, said Nasrallah, was Ein Shemer, a military airport used by Israeli drones.
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He also appeared to suggest Hezbollah's retaliation for Shukr's killing was over, saying "if the result is satisfactory" then its response "has been accomplished".
An AFP photographer in Acre, an Israeli city 20 kilometres (12 miles) from the border, reported damage to three homes from a Hezbollah rocket that struck a roof, with shrapnel smashing windows and destroying a bed.
"There were explosions in the area of Haifa," said Abigail Levy, a resident of the coastal city further south. "I was stopped and was told not to go to the beach."
AFPTV footage from early Sunday showed dozens of interceptor rockets being launched into dense clouds above the Upper Galilee in northern Israel.
An AFP photographer saw a Hezbollah drone exploding into a huge fireball as it was intercepted by the Israeli Air Force.
Hezbollah announced two of its fighters had been killed, while its ally the Amal movement also reported the death of a member. No casualties were immediately reported in Israel.
Military spokesman Rear Admiral Daniel Hagari said Israel "was aware" of six militants "killed in the strikes".
Another military spokesman, Nadav Shoshani, said Hezbollah's strikes were "part of a larger attack that was planned and we were able to thwart a big part of it this morning".
The fighting disrupted air travel in Israel and Lebanon, with both British Airways and Air France among those suspending flights to Tel Aviv.
'Stop the escalation'
Yemen's Huthi rebels, one of several Iran-backed groups that have been drawn into the Gaza war's periphery, hailed the Hezbollah attack and declared that their own retaliation was "definitely coming".
The fighting between Israeli forces and Hezbollah has killed hundreds, mostly in Lebanon, and displaced tens of thousands of residents on both sides of the border.
Lebanese Prime Minister Najib Mikati told an emergency cabinet meeting he was in contact with "Lebanon's friends to stop the escalation".
General Charles Brown, the most senior officer in the US military, arrived in Israel on Sunday evening to meet his Israeli counterpart Lieutenant General Herzi Halevi, the Israeli military said.
The United States is Israel's top military supplier.
A US defence official said Washington had helped track the Hezbollah barrage although it was not involved in shooting down any drones or rockets or in the strikes on Lebanon.
The Flightradar24 tracking website on Sunday afternoon showed a US Navy surveillance drone had been flying over nearby Mediterranean waters.
Gaza talks
Hamas hailed Hezbollah's Sunday attack as "a slap in the face" for Israel, and the Palestinian movement on Sunday night said it fired a rocket toward Tel Aviv.
Israel's military said it landed in an "open area" south of the city.
In the leadup to Sunday's major exchange, Western and Arab diplomats had sought to head off regional retaliation, stressing the urgency of reaching a Gaza ceasefire and hostage release deal.
Egypt's President Abdel Fattah al-Sisi, whose officials have been mediating Gaza truce talks for months alongside the US and Qatar, "warned of the dangers of a new front opening in Lebanon" and called for progress in the talks to enable a "path to calm and stability in the region" his office said.
A Hamas official said on Sunday the group's delegation had left the Egyptian capital after meeting with mediators.
In Gaza, witnesses said battles raged in the area of Deir al-Balah, in the territory's central region.
Hamas's October 7 attack on southern Israel resulted in the deaths of 1,199 people, most of them civilians, according to an AFP tally based on Israeli official figures.
Israel's retaliatory military campaign has killed at least 40,405 people in Gaza, according to the Hamas-run territory's health ministry, which does not break down civilian and militant deaths. The UN rights office says most of the dead are women and children.
Out of 251 hostages seized by Palestinian militants in their attack, 105 remain in Gaza including 34 the Israeli military says are dead.