Lebanon's health minister said nine people were killed and 2,800 wounded Tuesday when pagers used by Hezbollah members exploded across the country.
The sons of Hezbollah lawmakers Ali Ammar and Hassan Fadlallah were among the dead, a source close to the group told AFP, requesting anonymity to discuss sensitive matters.
The blasts "killed nine people, including a girl", minister Firass Abiad said in a casualty update.
"About 2,800 people were injured, about 200 of them critically" with injuries mostly reported to the face, hands and stomach, he added.
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 Beirut was also wounded in a pager explosion but his injuries were not serious, state media reported.
In neighbouring Syria, 14 people were wounded "after pagers used by Hezbollah exploded," Britain-based war monitor, the Syrian Observatory for Human Rights said.
The Israeli military said it had "no comment," when contacted by AFP about the pager blasts.
The blasts came just hours after Israel announced it was broadening the aims of the war to include its fight against Hezbollah along its border with Lebanon.
Hezbollah blamed Israel for the blasts and warned it would be punished.
"We hold the Israeli enemy fully responsible for this criminal aggression," the group said in a statement, adding that Israel "will certainly receive its just punishment for this sinful aggression".
The afternoon blasts hit several Hezbollah strongholds across Lebanon, in the first such incident since the group began trading near-daily fire with Israel in support of ally Hamas.
"Hundreds of Hezbollah members were injured by the simultaneous explosion of their pagers" in the group's strongholds in Beirut's southern suburbs, in south Lebanon and in the eastern Bekaa Valley, a Hezbollah source said, requesting anonymity.
Earlier Tuesday, Israel announced it was broadening the aims of the war sparked by the Hamas attacks to include its fight against Hezbollah along its border with Lebanon.
To date, Israel's objectives have been to crush Hamas and bring home the hostages seized by Palestinian militants during the October 7 attacks that sparked the war.
"The political-security cabinet updated the goals of the war this evening, so that they include the following section: the safe return of the residents of the north to their homes," Israeli Prime Minister Benjamin Netanyahu's office said in a statement.
Since October, the unabating exchanges of fire between Israeli troops and Hamas ally Hezbollah in Lebanon have forced tens of thousands of people on both sides of the border to flee their homes
Not formally declared as a war, the exchanges of fire between Israeli troops and Hezbollah have killed hundreds of mostly fighters in Lebanon, and dozens on the Israeli side.
Hezbollah had instructed its members to avoid mobile phones after the Gaza war began and to rely instead on its own telecommunications system to prevent Israeli breaches.
On Monday, Israeli Defence Minister Yoav Gallant warned that failing a political solution, "military action" would be "the only way left to ensure the return of Israel’s northern communities".
Before the wave of pager explosions, Israel said it had killed three Hezbollah members in a strike on Lebanon.
'Fundamental change'
"The possibility for an agreement is running out as Hezbollah continues to tie itself to Hamas," Gallant's office quoted him as telling visiting US envoy Amos Hochstein.
Netanyahu later told Hochstein he was seeking a "fundamental change" in the security situation on Israel's northern border.
Hezbollah deputy chief Naim Qassem said at the weekend that his group had "no intention of going to war", but that "there will be large losses on both sides" in the event of all-out conflict.
"Without a ceasefire in Gaza, there will be no agreement on the question of the border with Lebanon," said Michael Horowitz, of the Le Beck International security consultancy.
Israel's aim in expanding the war would be to "create a 'buffer zone' in southern Lebanon", Horowitz added.
Hamas, meanwhile, said it was readying for more war, with assistance from fighters and support from across the region.
In a letter to the group's Yemeni allies, the Iran-backed Huthi rebels, Hamas chief Yahya Sinwar said: "We have prepared ourselves to fight a long war of attrition."
"Our combined efforts with you... will break this enemy and inflict defeat on it", Sinwar said.
Blinken in Egypt
US Secretary of State Antony Blinken was due back in the region to try to revive stalled ceasefire talks for the Israel-Hamas war in Gaza.
After months of mediated negotiations failed to pin down a ceasefire, Washington said it was still pushing all sides to finalise an agreement.
US State Department spokesman Matthew Miller said Blinken would discuss during a visit to Egypt "ongoing efforts to reach a ceasefire in Gaza that secures the release of all hostages, alleviates the suffering of the Palestinian people, and helps establish broader regional security".
US officials have expressed increasing frustration with Israel as Netanyahu has publicly rejected US assessments that a deal is nearly complete and has insisted on an Israeli military presence on the Egypt-Gaza border.
Mounting pressure has failed to sway him to agree to a hostage release deal that has wide support from the Israeli public.
'Everything that was beautiful'
The October 7 attack 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.
On Tuesday, UN member states will debate a draft resolution demanding an end to the Israeli occupation of all Palestinian territories within 12 months.
General Assembly resolutions are not binding, but Israel has already denounced the new text as "disgraceful". In Gaza, rescuers said several Israeli air strikes killed at least seven people overnight.