The Lebanese armed group Hezbollah has launched more than 200 rockets and attack drones into northern Israel, in response to the killing of one of its senior commanders.
Israel’s military said one of its officers was killed in the barrage, which started a number of fires.
The military also said it had targeted Hezbollah “military structures” and other targets in southern Lebanon in response.
Lebanese media reported that one person was killed in an Israeli drone strike in the town of Houla.
The latest barrage, which followed one comprising 100 rockets on Wednesday afternoon, was one of the biggest so far in the nine months of cross-border violence which have raised fears of an all-out war.
The Hezbollah commander killed in an Israeli air strike near the southern Lebanese city of Tyre, Mohammed Nimah Nasser, was one of the most senior figures in the group to have been killed in the conflict.
The Israeli military said Nasser commanded Hezbollah’s Aziz Unit, which is responsible for launching rockets from south-western Lebanon, and accused him of directing a “large number of terror attacks”.
It also described him as “the counterpart” of Taleb Sami Abdullah, the commander of another unit whose killing last month prompted Hezbollah to launch more than 200 rockets and missiles into northern Israel in a single day.
There have been almost daily exchanges of fire across the Israel-Lebanon border since the day after the start of the war between Israel and Hamas in Gaza on 7 October.
Hezbollah has said it is acting in support of the Palestinian group that is also backed by Iran. Both groups are proscribed as terrorist organisations by Israel, the UK and other countries.
So far, more than 400 people have been reported killed in Lebanon, the vast majority of them Hezbollah fighters, and 25 people in Israel, mostly soldiers.
The Israeli Prime Minister Benjamin Netanyahu promised to restore security in northern Israel.
“In the tough campaign against Lebanon we have set a principle – whoever harms us is a dead man. We are making that a reality in practice,” he said on Thursday.
The hostilities have also displaced tens of thousands of people from border communities in northern Israel and southern Lebanon.
“The response to the assassination of the dear leader Hajj Abu Nimah [Nasser]… started last night and quickly,” senior Hezbollah official Hashem Safieddine warned at Nasser’s funeral in Beirut on Thursday.
“This series will continue to target new sites that the enemy did not imagine would be hit.”
A spokeswoman for the UN peacekeeping force in Lebanon, Unifil, said the exchanges were now extending deeper into both sides of the border, and called on both Israel and Hezbollah to show restraint.
“We’re very concerned… because any exchange, any incident, can escalate into something greater if there is a misunderstanding,” Kandice Ardiel told the BBC.
There has been a flurry of diplomatic efforts to de-escalate tensions in recent weeks, with the UN and US warning of the potentially catastrophic consequences of a war that could also draw in Iran and other allied groups.
Israeli officials have repeatedly warned that they are ready for a war if diplomacy fails. Defence Minister Yoav Gallant said on Wednesday that the military would soon be ready to “take any action required in Lebanon, or to reach an arrangement from a position of strength”.
Hezbollah, which is seen as a significantly superior foe to Hamas, has said it does not want a full-out war with Israel and that it will observe in Lebanon any ceasefire between Israel and Hamas in Gaza. But it has also warned Israel that it would fight “without rules” if there was a war.
