Lebanon's Hezbollah has confirmed its leader Sayyed Hassan Nasrallah has been killed.
The group said in a statement on Saturday it would continue its battle against Israel "in support of Gaza and Palestine, and in defence of Lebanon and its steadfast and honourable people".
Israel said earlier on Saturday it had killed Nasrallah in an air strike in Beirut's southern suburbs a day earlier.
Hezbollah's Al-Manar TV started airing Koran verses after the announcement of Nasrallah's death while Palestinian group Hamas said
in a statement it mourned Nasrallah's death.
A towering figure in the Tehran-backed "Axis of Resistance" who helped project Iranian influence across the Middle East, Nasrallah's death will mark a major blow not only to Hezbollah but to Iran.
The Israeli military said Nasrallah was eliminated in a "targeted strike" on the group's underground headquarters beneath a residential building in Dahiyeh - a Hezbollah-controlled southern suburb of Beirut.
It said another top Hezbollah leader, Ali Karaki, and other commanders were also killed.
"The strike was conducted while Hezbollah’s senior chain of command were operating from the headquarters and advancing terrorist activities against the citizens of the State of Israel," it said.
Friday's air strike on Dahiyeh shook Beirut.
A security source in Lebanon said the attack - a quick succession of massively powerful blasts - had left a crater at least 20 metres deep.
It was followed on Saturday by further air strikes on Dahiyeh and other parts of Lebanon.
Residents have fled Dahiyeh, seeking shelter in downtown Beirut and other parts of the city.
Hezbollah also continued its cross-border rocket fire, setting off sirens and sending residents running for shelter deep inside Israel.
Israeli missile defences blocked some of them and there was no immediate report of injuries.
The escalation has increased fears the conflict could spin out of control, potentially drawing in Iran, Hezbollah's principal backer, as well as the US.
Lebanon's transport and public works ministry asked an Iranian plane not to enter Lebanese air space after Israel warned air traffic control at the Beirut airport on Friday that it would use "force" if the plane landed, a Lebanese transport ministry source said.
The source said it was not clear what was on the plane.
Late on Friday, Israeli military spokesperson Rear Admiral Daniel Hagari said Israeli air force planes were "patrolling the area of the Beirut airport" and would not allow "hostile flights with weapons to land" there.
"We know about Iranian arms transfers to Hezbollah and are thwarting them," he said.
Hezbollah has fired hundreds of rockets and missiles at targets in Israel, including Tel Aviv.
The group said it had fired more on Saturday.
Israel's air defence systems have ensured the damage has so far been minimal.
The Israeli military said the country was on high alert for a broader conflict and it hoped Nasrallah's death would cause the group to change course.
"We hope this will change Hezbollah's actions," Lieutenant Colonel Nadav Shoshani said in a media briefing.
But he said it would still take time to degrade Hezbollah's capabilities.
"It's safe to assume that they are going to continue carrying out their attacks against us or try to," he said.
Hours before the latest barrage, Netanyahu told the United Nations that his country had a right to continue the campaign.
"As long as Hezbollah chooses the path of war, Israel has no choice, and Israel has every right to remove this threat and return our citizens to their homes safely," he said.
Several delegations walked out as Netanyahu approached the lectern.
He later cut short his New York trip to return to Israel.
Lebanese health authorities confirmed six dead and 91 wounded in the initial attack on Friday - the fourth on Beirut's Hezbollah-controlled southern suburbs in a week and the heaviest since a 2006 war.
The toll appeared likely to rise much higher.
There was no word on casualties from the later strikes.
Israeli strikes have killed more than 700 people in the past week, Lebanese authorities said.
The number of people in Lebanon displaced by the conflict now stands at more than 200,000.
Israel says it aims to allow tens of thousands of residents evacuated from communities in northern Israel to return to their homes safely.
