The head of Hezbollah's operations centre has reportedly survived an Israeli strike targeting him.
Two security sources have told Reuters that Mushin Shukr was not killed in the attack on Beirut's southern suburbs, a stronghold of the militant group.
At least one person has been confirmed as being killed.
Israel's military claimed responsibility for the strike, saying they were targeting the person responsible for a rocket attack on the Golan Heights at the weekend, which killed 12 young people.
A loud blast was heard and a plume of smoke could be seen rising above the southern suburbs - a stronghold of the Iran-backed Lebanese armed group Hezbollah - at around 7:40pm (4.40am NZ time), a Reuters witness said.
Lebanon's state-run national news agency said an Israeli air strike had targeted the area around Hezbollah's Shura Council in the Haret Hreik neighbourhood of the capital.
Reuters reported the Lebanese prime minister said the country planned to file a complaint to the United Nations, and hoped for a "proportionate response" from Hezbollah "so that this wave of killing will stop".
Beirut has been on edge for days ahead of an anticipated Israeli attack in reprisal for the rocket strike on the Israeli-occupied Golan Heights on Saturday that killed the 12 youngsters in a football field in a Druze village. Hezbollah has denied involvement in that attack.
In a statement, the Israeli military said it had conducted "a targeted strike in Beirut on the commander responsible for the murder of the children in Majdal Shams and the killing of numerous additional Israeli civilians". Details would follow.
Earlier on Tuesday, more rocket fire from south Lebanon killed a civilian in a kibbutz in northern Israel, medics said.
Shortly before the explosion in south Beirut, the Israeli military said 15 projectiles had been fired across the Lebanese border within the past few hours, with impacts in parts of the Upper Galilee region. No injuries were reported.
Israel's air force had just hit a Hezbollah observation post and "terror infrastructure" in south Lebanon, it added.
Escalation concerns
As diplomats sought to contain the fallout, US Defense Secretary Lloyd Austin said he did not believe a fight was inevitable between Hezbollah and Israel, though he remained concerned about the potential for escalation.
Hezbollah and Israel, which last fought each other in a major war in 2006, have been trading fire since the eruption of the Gaza war in October, after Hezbollah began firing at Israeli targets in what it says is solidarity with the Palestinians.
The hostilities have mostly been limited to the frontier region and both sides have previously indicated they do not seek a wider confrontation even as the conflict has prompted worry about the risk of a slide towards war.
In the latest exchanges of fire on Tuesday, the Israeli military said 10 rockets had been fired from Lebanon and one hit Kibbutz Hagoshrim, causing one casualty. Israel's ambulance service said the 30-year-old male died of shrapnel wounds.
Israel said it hit some 10 Hezbollah targets in south Lebanon overnight and killed one Hezbollah fighter - attacks which appeared to be in keeping with the pattern of the last nine months. Hezbollah confirmed one of its fighters was killed.
- Reuters / RNZ