Israeli warplanes carried out dozens of strikes across southern Lebanon late on Thursday, hours after Hassan Nasrallah, Hezbollah’s leader, threatened “tough retribution and just punishment” for the wave of attacks that targeted the organisation with explosives hidden in pagers and walkie-talkies. The Israeli military said it had hit hundreds of rocket launchers which it said were about to be used “in the immediate future”. The bombardment included more than 52 strikes across southern Lebanon, the country’s state news agency NNA said. Three Lebanese security sources told the Reuters news agency that they were the heaviest aerial strikes since the conflict began in October. As Israeli jets roared over Beirut in a show of force earlier in the day, Nasrallah threatened retribution against Israel “where it expects it and where it does not”. On Tuesday, thousands of pagers used by Hezbollah exploded simultaneously, killing 12 people, including two children, and wounding up to 2,800 others across Lebanon. A day later, 25 people were killed and more than 450 wounded when walkie-talkies exploded in supermarkets, on streets and at funerals, stoking fears that a full-blown war between Hezbollah, which is backed by Iran, and Israel could be imminent. There was no comment from Israel, which hours before Tuesday’s explosions had announced it was broadening the aims of its war in Gaza to include the return of northern residents who had been evacuated from their homes due to attacks by Hezbollah. Nasrallah admitted that the explosive attacks – the biggest security breach for Hezbollah since its foundation in the 1980s – had been a major blow to the organisation. The attacks “crossed all red lines”, Nasrallah said, appearing in front of a featureless red background at an unidentified location. “The enemy went beyond all controls, laws and morals.” As tensions in the Middle East spiralled, senior diplomats from the US, Britain, Germany, France and Italy met on Thursday in Paris before a UN security council meeting planned for Friday. Antony Blinken, the US secretary of state, was to join his counterparts in the French capital after discussing the possibility of a Gaza truce in Cairo. US President Joe Biden believes there can still be a diplomatic resolution to escalating tensions between Israel and Hezbollah, his spokesperson said. The White House warned all sides against “an escalation of any kind”. The Lebanese foreign minister, Abdallah Bou Habib, warned that the “blatant assault on Lebanon’s sovereignty and security” was a dangerous development that could “signal a wider war”. The Israel Defense Forces’ chief of staff, Lt Gen Herzi Halevi, announced on Thursday that Israeli battle plans for the northern front had been “completed and approved”. On Wednesday, the Israeli defence minister, Yoav Gallant, described “the start of a new phase in the war” triggered by the Hamas attacks into Israel last October. The retired Brig Gen Amir Avivi, who leads the Israel Defense and Security Forum, which is a group of hawkish former military commanders, said: “There’s a lot of pressure from the society to go to war and win. Unless Hezbollah tomorrow morning says: ‘OK, we got the message, we’re pulling out of south Lebanon,’ war is imminent.” The Lebanese army said on Thursday it was blowing up pagers and suspicious telecom devices in controlled blasts in different areas. It called on citizens to report any suspicious devices. Lebanese authorities banned walkie-talkies and pagers from being taken on flights from Beirut airport until further notice, the National News Agency reported. Such devices were also banned from being shipped by air. Nasrallah’s speech on Thursday was keenly watched. Analysts said the Hezbollah leader needed to show defiance of Israel without committing to further escalation, which could lead to a war that Hezbollah’s sponsors in Tehran have sought to avoid. He also needed to rally his demoralised followers. Magnus Ranstorp, a terrorism expert at the Swedish Defence University and a pioneer of western studies of Hezbollah, said: “This is a huge humiliation for an organisation that prides itself on its security. They were lured into a trap … There were some civilian casualties, but most were Hezbollah people who will now be out of action for some time.” Hezbollah is a keystone member of Iran’s “axis of resistance”, which includes Hamas, the Houthis and other militant groups across the Middle East. Iran’s Revolutionary Guards commander, Hossein Salami, told Nasrallah on Thursday that Israel would face “a crushing response from the axis of resistance”, according to Iranian state media. In Israel, a man whom security forces said they arrested for plotting assassinations against senior political figures has been named as 73-year-old Moti Maman. Maman, from Ashkelon, near the Gaza Strip, was arrested last month and indicted on Thursday. The Shin Bet internal security service and the Israeli police have claimed that Iran was backing the plot to kill senior defence officials and possibly the prime minister, Benjamin Netanyahu. The preliminary findings of a Lebanese investigation into the blasts were that the pagers had been booby-trapped, a security official said. “Data indicates the devices were pre-programmed to detonate and contained explosive materials planted next to the battery,” the official said, requesting anonymity to discuss sensitive matters. A source close to Hezbollah, asking not to be identified, said the pagers were “recently imported” and appeared to have been “sabotaged at source”. After reports that the pagers had been ordered from a Taiwanese manufacturer, Gold Apollo, the company said they had been produced by its Hungarian partner BAC Consulting KFT, which has a licence to use its brand. A government spokesperson in Budapest said the company was “a trading intermediary, with no manufacturing or operational site in Hungary”. Icom, the Japanese communications equipment maker whose walkie-talkies are thought to have been detonated on Wednesday, said the devices may have been a discontinued model containing modified batteries. Hezbollah has traded near-daily cross-border fire with Israel since Hamas’s 7 October attacks sparked the war in Gaza. In his speech, Nasrallah vowed to continue the conflict with Israel until a ceasefire in Gaza was reached. “The Lebanese front will not stop until the aggression on Gaza stops”, despite “all this blood spilt”, he said. Israel said on Thursday it had bombed six Hezbollah “infrastructure sites” and a weapons storage facility in southern Lebanon, a stronghold of the organisation. Eight people were reported to have been injured by antitank missiles fired by Hezbollah into northern Israel, and two were hurt in a drone attack. Since October, more than 500 people have been killed in Lebanon by Israeli strikes, most of them fighters with Hezbollah and other armed groups but also more than 100 civilians. In northern Israel, at least 23 soldiers and 26 civilians have been killed by strikes from Lebanon. About 60,000 Israelis were evacuated from their homes along the contested border with Lebanon and have been unable to return for fear of being targeted by Hezbollah. In a separate development on Thursday, Israeli media reported that Israel had submitted a new ceasefire proposal to the US, under which all hostages held in Gaza would be released at the same time in exchange for ending the war. Israel would also agree that the Hamas leader, Yahya Sinwar, along with his family and thousands of operatives, could leave Gaza for a third country “through a safe passage”. There has been no official reaction to the reports.