The Israeli military said it killed high-ranking Hezbollah official Nabil Kaouk in a strike in a southern Beirut suburb on Saturday.
Sunday's announcement came a day after Hezbollah confirmed the killing of leader Hassan Nasrallah.
Kaouk is the deputy head of Hezbollah’s Central Council. He also served as Hezbollah’s military commander in south Lebanon from 1995 until 2010.
In 2020, the US Treasury sanctioned Kaouk and another member of Hezbollah’s council, Hassan al-Baghdadi.
Israel said on Sunday it was carrying out new air raids against "dozens" of Hezbollah targets in Lebanon, after killing Nasrallah.
Hezbollah confirmed on Saturday that its leader Nasrallah was killed in an Israeli strike a day earlier on Beirut's southern suburbs, dealing a massive blow to the group he had led for decades.
His killing marks a sharp escalation in nearly a year of tit-for-tat cross-border fire between Hezbollah and Israel, and risks plunging the whole region into a wider war.
Israel continued to pound Lebanon on Sunday, with the military saying it "attacked dozens of terrorist targets in the territory of Lebanon in the last few hours".
The strikes targeted "buildings where weapons and military structures of the organization were stored".
The military has attacked hundreds of Hezbollah targets throughout Lebanon since Saturday, it said, as it seeks to disable the group's military operations and infrastructure.
Hezbollah began low-intensity cross-border strikes on Israeli troops a day after its Palestinian ally Hamas staged its unprecedented attack on Israel on October 7, triggering war in the Gaza Strip.
Israel has raised the prospect of a ground operation against Hezbollah, prompting widespread international concern.
Following Nasrallah's death, Netanyahu said Israel had "settled the score" for the killing of Israelis and citizens of other countries, including Americans.
- 'Unjust bloodshed' -
Nasrallah was the face of Hezbollah, enjoying cult status among his supporters.
Israeli military spokesman Daniel Hagari said: "His elimination makes the world a safer place."
But Iran's First Vice President Mohammad Reza Aref denounced the "unjust bloodshed" and threatened that Nasrallah's killing will bring about Israel's "destruction".
Hamas condemned Nasrallah's killing as a "cowardly terrorist act".
Lebanon, Iraq, Iran and Syria all declared public mourning, while Yemen's Houthi group said they fired a missile at Israel's Ben Gurion airport on Saturday, hoping to hit it as Netanyahu returned from a trip to New York.
US President Joe Biden -- whose government is Israel's top arms supplier -- said it was a "measure of justice", while Kamala Harris, who is running to replace him in the White House, called Nasrallah "a terrorist with American blood on his hands".
Iran called for an emergency meeting of the UN Security Council in protest at Nasrallah's killing.
In the letter, Iran's UN envoy Amir Saeid Iravani called on the Security Council to "take immediate and decisive action to stop Israel's ongoing aggression" and prevent it "from dragging the region into full-scale war".
Analysts told AFP that Nasrallah's death leaves Hezbollah under pressure to deliver a response.
"Either we see an unprecedented reaction by Hezbollah... or this is total defeat," said Heiko Wimmen of the International Crisis Group think tank.
- Mass displacement -
More than 700 people have been killed in Israeli strikes on Lebanon, according to health ministry figures, since the bombardment of Hezbollah strongholds began earlier this month.
Strikes on Saturday killed 33 people and wounded 195, the ministry said.
Most of the deaths in Lebanon came on Monday, the deadliest day of violence since the country's 1975-1990 civil war.
UN refugee chief Filippo Grandi said "well over 200,000 people are displaced inside Lebanon" and more than 50,000 have fled to neighboring Syria.
Hundreds of families spent the night into Saturday outside as air strikes pounded south Beirut.
"I didn't even pack any clothes, I never thought we would leave like this and suddenly find ourselves on the streets," south Beirut resident Rihab Naseef, 56, told AFP.
Meanwhile, air strikes of unknown origin in eastern Syria killed 12 pro-Iran fighters and wounded a large number of people, a war monitor said Sunday.
The strikes, in and around the city of Deir Ezzor and near the border with Iraq, were not immediately claimed but had targeted military positions, the Syrian Observatory for Human Rights said.
- Israel to 'remove this threat' -
Netanyahu has vowed to keep fighting until the border with Lebanon is secured.
"Israel has every right to remove this threat and return our citizens to their homes safe," he said.
Diplomats have said efforts to end the war in Gaza were key to halting the fighting in Lebanon and bringing the region back from the brink.
Hamas's October 7 attack on Israel resulted in the deaths of 1,205 people, mostly civilians, according to an AFP tally based on Israeli official figures that include hostages killed in captivity.
Of the 251 hostages seized by militants, 97 are still held in Gaza, including 33 the Israeli military says are dead.
Israel's retaliatory military offensive has killed at least 41,586 people in Gaza, most of them civilians, according to figures provided by the Hamas-run territory's health ministry. The UN has described the figures as reliable.
