According to Lebanese authorities, at least 182 people have been killed and 890 injured - figures that are feared to rise.
And Israeli Prime Minister Benjamin Netanyahu says more could come. In a televised speech on Wednesday night, he said Israel has "additional goals to achieve."
We will achieve these, either through agreements or by resuming the fighting.
Netanyahu says Israel is behind the ceasefire agreement, but insists it does not include Lebanon.
Hezbollah threatens to respond
Hezbollah, for its part, is now asserting its "right" to respond to Israel's deadly wave of airstrikes on Lebanon.
"We affirm that the blood of the martyrs and the wounded will not be spilled in vain," the Iran-backed movement said in a statement.
Israel announced on Wednesday afternoon that it had launched "over a hundred strikes in ten minutes" against Lebanon. Several hundred Hezbollah members were targeted in the "surprise attack," according to Israeli Defense Minister Israel Katz.
It is the largest attack against Hezbollah since the outbreak of the conflict, the Israeli military wrote in a statement.
Panic in the streets
Lebanon's Prime Minister appeals to the outside world to put an end to the attacks.
The attacks represent a "complete disregard" for international law, writes Lebanese Prime Minister Nawaf Salam on X.
"All friends of Lebanon are called upon to help stop these aggressions by all means at their disposal," he adds.
Major attacks have taken place in Beirut, among other places. Black smoke rises over several parts of the capital, where panic erupted in the streets as bombs fell in busy traffic areas. Among the targets attacked are several apartment buildings.
Two-week ceasefire between Iran and the US covers their allies on all fronts - "including Lebanon," writes Pakistani Prime Minister Shehbaz Sharif, who mediated between the US and Iran, on X.
Invasion on the ground
According to unconfirmed reports in the semi-official Iranian news agency Tasnim, Iran, for its part, will withdraw from the ceasefire agreement if Israel continues its attacks in Lebanon.
Since the start of the conflict, Israel has entered southern Lebanon in a ground invasion, bombed targets in Beirut, and more than a million people have been displaced.
Israel says it is establishing an expanded security zone in the neighboring country, in a new occupation of Lebanese territory that is planned to continue even after an end to the fighting.
