At least nine people died and 2,750 were wounded when pagers used by Hezbollah members exploded across the country, according to Lebanon's health ministry.
The ministry updated the figures, having earlier reported 11 deaths and 4,000 injuries.
Hezbollah said that Israel is "fully responsible" for the blasts, adding that it will get "its fair punishment", according to a statement released by the militant group.
The explosions hit locations in several Hezbollah strongholds around Lebanon this afternoon.
The Israeli military said it had "no comment" regarding the blasts.
The sons of Hezbollah politicians Ali Ammar and Hassan Fadlallah were among the dead, a source close to the group said, requesting anonymity to discuss sensitive matters.
The 10-year-old daughter of a Hezbollah member was killed in east Lebanon's Bekaa Valley when his pager exploded, her family and a source close to the group said.
Iran's ambassador to Lebanon was also wounded in a pager explosion but his injuries were not serious.
"Iranian ambassador to Lebanon Mojtaba Amani was injured in a pager explosion," Iranian state television said, adding that his wounds were "superficial" and that he was "conscious and in no danger".
In neighbouring Syria, 14 people were wounded "after pagers used by Hezbollah exploded," UK-based war monitor, the Syrian Observatory for Human Rights said.
A photographer in Beirut's southern suburbs showed ambulances rushing injured Hezbollah members to hospitals in the area.
Dozens of people were also reported wounded in similar incidents in the Bekaa Valley in east Lebanon.
In Lebanon's south, an AFP correspondent reported dozens of ambulances rushing between the cities of Tyre and Sidon in both directions, with hospitals in both cities cordoned off.
In a statement, the Lebanese health ministry asked "all hospitals in... areas near the locations of the injured, to be on high alert and raise their level of preparedness", and "all health workers to urgently go to their workplaces" to assist.
The Lebanese Red Cross said it was on "high alert" in a statement shared on X.
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Lebanon's official National News Agency reported "an unprecedented enemy security incident" with "hand-held pagers detonating" in several regions.
Regional broadcasters carrying CCTV footage which showed what appeared to be a small handheld device placed next to a grocery store cashier where an individual was paying spontaneously exploding.
In other footage, an explosion appeared to knock out someone standing at a fruit stand at a market area.
Lebanon's crisis operations centre, which is run by the health ministry, asked all medical workers to head to their respective hospitals to help cope with the massive numbers of wounded coming into for urgent care.
It said health care workers should not use pagers.
Hezbollah had asked its members to avoid using mobile phones after the Gaza war began to avoid Israeli breaches of the technology.
Hezbollah members communicate through their own telecommunications system.
Hezbollah fired missiles at Israel immediately after the 7 October attacks by Hamas gunmen on Israel.
The group has been exchanging fire constantly with Israel ever since, while avoiding a major escalation as war rages in Gaza to the south.
The Israeli military declined to comment on enquiries about the detonations.
Israel expands war goals with truce efforts ongoing
Regular exchanges of fire between Hezbollah and Israel have killed hundreds of mostly fighters in Lebanon, and dozens of civilians and soldiers on the Israeli side since the war broke out.
Tens of thousands of people have been displaced from towns and villages on both sides of the border by the hostilities.
Hezbollah officials have said the group would stand down if a Gaza ceasefire were reached and that group has "no intention of going to war", but if Israel does "unleash" one "there will be large losses on both sides".
Yesterday, Israel's Prime Minister Benjamin Netanyahu expanded the country's goals for the war in Gaza, vowing to allow Israelis who fled areas near the Lebanon border to return to their homes.
Qatar's foreign ministry said efforts to forge a Gaza truce were "ongoing", after several rounds of talks aimed at ending the now 11-month war ended without a breakthrough.
"The efforts are still ongoing and channels of communication remain open... the goals and visits and meetings are ongoing," ministry spokesman Majed al-Ansari told reporters.
Months of behind-the-scenes negotiations mediated by Qatar, Egypt and the United States have failed to halt the fighting between Hamas and Israel, apart from a one-week truce beginning in late November.
Recent mediation in Doha and Cairo has been based on a framework laid out in May by US President Joe Biden and a "bridging proposal" presented to the warring parties in August.
US Secretary of State Antony Blinken is due to visit Egypt this week to "discuss ongoing efforts to reach a ceasefire", his tenth trip to the region since 7 October.
After in-person talks last month in Egypt and Qatar broke up without a final agreement, Washington indicated that mediators were preparing to present another adapted framework for a ceasefire.
US State Department spokesman Matthew Miller said Washington was working "expeditiously" on a new proposal.
Mr Ansari declined to comment on whether any further proposal had been relayed to Israel or Hamas.
"When it comes to the possibility of a deal taking place anytime soon, of course we remain hopeful at every juncture," he said.
"I can't comment on the prospects of a deal taking place right now but I can tell you that we remain hopeful and we continue with our efforts."
Hamas said its delegation met Qatari and Egyptian mediators in Doha last week to discuss a truce and potential hostage and prisoner exchange, again without indicating that any breakthrough had been reached.
The 7 October attack by Palestinian militants on southern Israel that sparked the war resulted in the deaths of 1,205 people, mostly civilians, according to an AFP tally based on official Israeli figures.
Militants also seized 251 hostages, 97 of whom are still held in Gaza, including 33 the Israeli military says are dead.
Israel's retaliatory military offensive has killed at least 41,252 people in Gaza, according to the Hamas-run territory's health ministry, which does not provide a breakdown of civilian and militant deaths.
