• Israeli Prime Minister Benjamin Netnyahu said the killing of Hassan Nasrallah was a necessary step of achieving Israel's defensive goals but was not enough to end the war.
• Nasrallah, 64, was regarded as one of the most influential figures in the Middle East and has played a key role in transforming Hezbollah into a major military and political force.
• Nasrallah led the Lebanon-based group since 1992, taking the reins after Israel assassinated the group's previous leader, Abbas al-Musawi.

Israeli Prime Minister Benjamin Netanyahu on Saturday commended the killing of Hezbollah leader Hassan Nasrallah and said his death would not be enough to end the proliferating conflict in the Middle East.

"We have some great achievements, but we haven't completed the task at hand yet," Netanyahu said, according to a translation by NBC News. "The devastating blows leveled at Hezbollah by the IDF will not be enough."

Hezbollah confirmed that Nasrallah was killed on Friday in an Israeli airstrike in the Lebanese capital of Beirut.

"There is no place in Iran, nor in the Middle East, where the long arm of Israel cannot reach," Netanyahu said.

A statement from Hezbollah also on Saturday said Nasrallah "has joined his great immortal martyr comrades." The confirmation came just a few hours after the Israeli army announced the killing of Nasrallah, after carrying out a large-scale attack on Lebanon the day before.

Israel's Defense Forces (IDF) said Nasrallah, who led the Iran-backed militant group for more than three decades, was killed on Friday as fighter jets conducted what it described as a "targeted strike" on Hezbollah's headquarters in Beirut.

Among other Hezbollah commanders, the IDF said Ali Karki, the commander of Hezbollah's southern front, was also killed in the strike.

The announcement marks what would be considered a monumental blow to Hezbollah after several months of conflict. The IDF said Nasrallah was the group's "central decision-maker" and "strategic leader."

Lebanese political analyst Ronnie Chatah said Saturday that the Hezbollah that had been able to wield power with absolute authority, grow to stand as the world's largest paramilitary force and become the world's most sophisticated terrorist organization, was now over.

"I think the symbolism cannot be overstated. This is, by far, the deepest psychological blow to this organization since its inception. Hezbollah cannot be the same without Hassan Nasrallah," he said, speaking before Hezbollah's confirmation of the death.

Chatah said what emerges in the coming months and years will be "something else," an organization that will remain intact, "albeit much smaller."

President Joe Biden on Saturday called Nasrallah's death from Israel's airstrike "a measure of justice for his many victims, including thousands of Americans, Israelis, and Lebanese civilians."

In the White House statement, Biden also doubled down on support for Israel and his ongoing calls for a ceasefire and hostage release deal in Gaza. He also reiterated his hope to deescalate the conflict in the Middle East, which is teetering on the brink of all-out regional war.

'A big void'

Nasrallah, 64, is regarded as one of the most influential figures in the Middle East and has played a key role in transforming Hezbollah into a major military and political force.

He has led the Lebanon-based group since 1992, taking the reins after Israel assassinated the group's previous leader, Abbas al-Musawi.

Hezbollah, which is recognized as a terrorist organization by the U.S., Britain, and other nations, is known to be driven by its violent opposition to Israel and its resistance to Western influence in the Middle East, according to the Council on Foreign Relations think tank.

Firas Maksad, a senior fellow at the Washington-based Middle East Institute think tank, said on Saturday that news of Nasrallah's killing would lead to "significant" regional ramifications.

"Nasrallah was the preeminent and most iconic Arab leader in Iran's regional axis. His killing is emblematic of a head-on confrontation between Israel and Iran over the future of Lebanon and the Levant. This is likely the begging of a coming clash and not the end," Maksad said.

"Locally, Nasrallah was also the most powerful leader [in] Lebanon's Shia community. His assassination leaves a big void and raises serious [questions] about the future role of the community within Lebanon's archaic sectarian system," he continued.

"In the short-term, it is likely to exacerbate political polarization and further contribute to the fragility of a country with weak central government, contributing to further unrest," Maksad said.

Tens of thousands of people on both sides of the Israel-Lebanon border have had to leave their homes as a result of the cross-border fire in the months following the Oct. 7 attack on Israel by Hamas. Hezbollah has expressed solidarity with the Islamist Palestinian group Hamas.

Israel's leaders have vowed that evacuated residents of northern Israel will be able to return to their homes. 

"Israel now awaits to see whether Iran will join retaliation on behalf of Hezbollah, leading to an even greater regional escalation," Nimrod Goren, a senior fellow for Israeli affairs at the Middle East Institute, told CNBC.

"But, recent developments also provide an opportunity for an off-ramp. After diminishing Hezbollah's power, Israel should finally be ready for a cease-fire in Gaza."

— CNBC's Emma Graham contributed to this report.