BEIRUT, Lebanon (AFP) — A second deadly wave of unprecedented explosions in the strongholds of Lebanon's Hezbollah left it in disarray on Thursday, hours before a major speech by its beleaguered leader Hassan Nasrallah.

The latest batch of device explosions killed 20 people and wounded more than 450 others on Wednesday, officials said, stoking fears of a full-blown war with Israel.

Walkie-talkies used by its members exploded in the latest blasts at Hezbollah's Beirut stronghold, a source close to the group said, with state media reporting similar detonations in south and east Lebanon.

AFPTV footage showed people running for cover when an explosion went off during a funeral for Hezbollah militants in south Beirut in the afternoon.

"The wave of enemy explosions that targeted walkie talkies... killed 20 people and wounded more than 450," Lebanon's health ministry said in a statement.

The blasts came a day after the simultaneous detonation of pagers used by Hezbollah killed 12 people, including two children, and wounded up to 2,800 others across Lebanon, in an unprecedented attack blamed on Israel.

There was no comment from Israel, which only hours before Tuesday's explosions had announced it was broadening the aims of its war in Gaza to include its fight against Hamas' ally Hezbollah.

"The center of gravity is moving northward," Israeli Defense Minister Yoav Gallant said during a visit to an air base on Wednesday. "We are at the start of a new phase in the war."

Amos Harel of the left-leaning Haaretz newspaper said the pager and walkie-talkie blasts had put "Israel and Hezbollah on the brink of all-out war."

The Israeli military also said on Thursday it struck six Hezbollah "terrorist infrastructure sites" and a weapons storage facility in southern Lebanon overnight.

The air force "struck Hezbollah terrorist infrastructure sites in the areas of 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 in southern Lebanon," a military statement said.

Out of this world

With tensions in the Middle East spiralling, senior diplomats from the United States, Britain, Germany, France and Italy will meet on Thursday in Paris, sources said, ahead of a United Nations Security Council meeting planned for Friday.

United States Secretary of State Antony Blinken will join his counterparts in the French capital after discussing the possibility of a Gaza war truce in Cairo.

The White House warned all sides against "an escalation of any kind."

"We don't believe that the way to solve where we're at in this crisis is by additional military operations at all," US National Security Council spokesperson John Kirby told reporters.

Iran-backed Hezbollah has traded near-daily cross-border fire with Israel since Hamas' 7 October attacks sparked the war in Gaza.

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."

Hezbollah said Israel was "fully responsible for this criminal aggression" and vowed revenge.

Iran's envoy to the United Nations said the country "reserves the right to take retaliatory measures" after its ambassador in Beirut was wounded.

The influx of so many casualties all at once overwhelmed medics.

At a Beirut hospital, doctor Joelle Khadra said "the injuries were mainly to the eyes and hands, with finger amputations, shrapnel in the eyes —some people lost their sight."

A doctor at another hospital in the Lebanese capital said he had worked through the night and that the injuries were "out of this world — never seen anything like it."

Among the dead was the 10-year-old daughter of a Hezbollah member, killed in east Lebanon's Bekaa Valley when her father's pager exploded, the family and a source close to the group said.