Israel bombed southern Lebanon on Thursday and said it had thwarted an Iranian-led assassination plot, a day after explosions of Hezbollah radios that came on the heels of blasts in booby trapped pagers, setting the foes hurtling towards war.

The sophisticated attacks on armed group Hezbollah's communications equipment, which killed 37 people and wounded around 3,000 over two days, sowed disarray in Lebanon, with panicked residents abandoning their mobile phones.

"This isn’t a small matter, it’s war. Who can even secure their phone now? When I heard about what happened yesterday, I left my phone on my motorcycle and walked away," said Mustafa Sibal on a street near central Beirut.

A distant roar in the skies could be heard in Beirut from what Lebanese state media said was Israeli jets breaking the sound barrier - a sound that has grown increasingly common in recent months.

Israel said its warplanes struck villages in southern Lebanon overnight, and a security source and Hezbollah's al-Manar TV reported airstrikes near the border resumed on Thursday just after midday.

Hand-held radios used by Hezbollah detonated on Wednesday across Lebanon's south. The Lebanese health minister raised the death toll, saying 25 people had been killed and 608 injured in the country's deadliest day since cross-border fighting erupted between the militants and Israel in parallel with the Gaza war last year.

The previous day, hundreds of pagers - used by Hezbollah to evade mobile phone surveillance - exploded at once, killing 12 people including two children, and injuring more than 2,300.

In a post on X, Lebanese Prime Minister Najib Mikati called on the United Nations Security Council to take a firm stand to stop Israel's "aggression" and "technological war" against his country.

Israel has not commented directly on the booby-trapped walkie-talkies and pagers, but multiple security sources have said the attacks were carried out by its spy agency Mossad.

Israel says its conflict with Hezbollah, like its war in Gaza against Palestinian militant group Hamas, is part of a wider regional confrontation with Iran, which sponsors both groups as well as armed movements in Syria, Yemen and Iraq.

On Thursday Israeli security forces announced that an Israeli businessman had been arrested last month after attending at least two meetings in Iran, where he discussed assassinating Prime Minister Benjamin Netanyahu, the defence minister or the head of the Shin Bet spy agency.

Last week, Shin Bet uncovered what it said was a plot by Hezbollah to assassinate former Defence Minister Moshe Ya'alon.

Israel has been accused of assassinations including a blast in Tehran that killed the leader of Hamas and another in a Beirut suburb that killed a senior Hezbollah commander within hours of each other in July.

Despite the events of the past few days, a spokesperson for the U.N. peacekeeping mission in southern Lebanon said the situation along the frontier had "not changed much in terms of exchanges of fire between the parties".

"There was an intensification last week. This week it is more or less the same. There are still exchanges of fire. It is still worrying, still concerning, and the rhetoric is high," the spokesperson, Andrea Tenenti, told Reuters.

Israel and Hezbollah have been exchanging fire across the Israeli-Lebanon border in parallel with the war Israel has waged in Gaza against Hamas, the Palestinian militant group whose fighters attacked Israel on Oct. 7.

Tens of thousands of people have had to flee the Israel-Lebanon border area on both sides. Netanyahu vowed on Wednesday to return the evacuated Israelis "securely to their homes".

SHIFTING FOCUS

The Israeli military said its overnight air strikes hit Hezbollah targets in Chihine, Tayibe, Blida, Meiss El Jabal, Aitaroun and Kfarkela in southern Lebanon, as well as a Hezbollah weapons storage facility in the area of Khiam.

Israeli media reported that a number of Israeli civilians had been wounded by anti-tank missile fire from Lebanon, but there was no official confirmation.

On Wednesday, Israeli Defence Minister Yoav Gallant said the war was moving into a new phase, with more resources and military units now being shifted to the northern border.

According to Israeli officials, the forces being deployed there include the 98th Division, an elite formation including commando and paratroop elements that has been fighting in Gaza.

Hezbollah launched missile barrages on Israel on the day after the Oct. 7 attack by Hamas, and since then there has been a constant exchange of fire that neither side has allowed to escalate into a full-scale war.

However, tens of thousands have been evacuated on both sides of the border, and there has been mounting pressure in Israel for the government to get the evacuees back home.