The attack which Israel says to have killed chief of staff Haytham Tabtabai in the southern suburbs of Beirut also killed four other people and injured 25.
Israel announced on Sunday evening that it had killed Haitham Tabatabai, who claims to be the chief of staff of Hezbollah, in an attack in the Lebanese capital, Beirut.
The attack in the southern suburbs of the Lebanese capital killed five people and wounded 28 others, according to local authorities.
It was the first Israeli strike in Beirut since last June.
Hezbollah had earlier announced that an Israeli resistance "figure" was likely killed in the attack, without giving further details.
"Hezbollah's leadership is studying the issue of the response and will make an appropriate decision. Today's attack in the southern suburbs opens the door to an escalation of attacks across Lebanon," Mahmoud Qamati, deputy chairman of Hezbollah's political council, said from the scene of the attack.
In a statement, Israeli Defence Minister Israel Katz said: "We will continue to act forcefully to prevent any threat to the residents of the north and the state of Israel."
Lebanese President Joseph Aoun condemned Sunday's attack and accused Israel of refusing to implement the end of the ceasefire agreement. He called on the international community to "intervene forcefully and seriously to stop the attacks against Lebanon and its people."
Tabatabai had led Hezbollah's elite Radwan unit.
He was considered the successor to Ibrahim Akil, who was killed in September 2024 in Israeli attacks that wiped out much of Hezbollah's senior leadership, including longtime leader Hassan Nasrallah.
The Israeli military said he "commanded most of Hezbollah's units and worked hard to bring them back to readiness for war with Israel."
Israel's foreign ministry said his killing came after repeated ceasefire violations by Hezbollah.