Israel announced Saturday that its forces killed Hassan Nasrallah, the powerful leader of the Lebanese militant and political group Hezbollah. This would represent a major escalation amid increasing hostilities on Lebanon's northern border.

An Israeli official said on Friday that Israeli forces targeted Nasrallah, who has led the Iran-backed militant group for the past three decades, in a large-scale attack on a southern Beirut suburb.

“Hassan Nasrallah will no longer be able to terrorize the world,” the Israel Defense Forces said in a post on X.

Hezbollah had yet to confirm early Saturday morning whether the 64-year-old Nasrallah had been killed, and NBC News was not immediately able to independently verify the claim.

Earlier on Friday, a Hezbollah spokesman said that Nasrallah, who was rarely seen in public, was not in any of the buildings attacked by Israeli forces and was “fine.” It was not clear whether that analysis had changed.

Under Nasrallah's leadership, Hezbollah became the most powerful Iranian-backed paramilitary group in the Middle East, with an arsenal of ballistic missiles aimed at Israel, and a powerful political player in Lebanon. The disciplined force has also trained other Iranian proxies in the region and fought in Syria to suppress forces trying to topple President Bashar al-Assad's regime.

He called for the “liberation” of Jerusalem, described Israel as a “Zionist entity” and praised Hamas’ attacks on Israel on October 7, 2023 as a “heroic, major and magnificent operation.”

Nasrallah had said that Hezbollah's ongoing missile and drone campaign against northern Israel, which began shortly thereafter, was carried out in solidarity with the Palestinians. Hezbollah has vowed to continue its campaign against Israel until it ends its nearly year-long offensive in Gaza.

Nasrallah was born in Beirut in 1960 into a poor Shiite family and grew up in the Karantina district. He studied theology and, after the civil war broke out in Lebanon, joined the Amal Movement, a Lebanese Shiite political and paramilitary organization with ties to Iran.

Nasrallah had traveled to Najaf, Iraq, one of Shiite Islam's holiest cities, where he studied at a seminary before returning to Lebanon and becoming commander for Amal in Beqaa.

He later became a founding member of Hezbollah, joining the group in 1982 following the Israeli invasion of Lebanon, which began on June 6 of that year.

Hezbollah was founded this year to fight against invading Israeli forces. Nasrallah rose to become the group's secretary general after his predecessor, Sayyed Abbas Musawi, was killed by Israeli forces in 1992, The Associated Press reported.

Under his leadership, Hezbollah, whose name means “Party of God” and is designated a terrorist organization by the United States, rose to prominence as it fought to drive Israel out of Lebanon until the country withdrew its forces in May 2000.

And his status was elevated even further after he led the group into a 34-day war with Israel in 2006 that ended with a United Nations-backed ceasefire. This conflict began when Hezbollah fired rockets at Israeli military bases and border villages and then captured two Israeli soldiers.

Ed Husain, a senior fellow at the Council on Foreign Relations focusing on the Middle East, said Israel's attack on Nasrallah could be viewed as a “proactive strategy to defend Israel” and should not come as a surprise.

“Israel no longer seems to be afraid of a direct clash with Iran,” Hussain said, adding: “Israel will not be afraid of a major operation.”

The IDF's claim that it assassinated Nasrallah came after its forces carried out airstrikes on Friday on Hezbollah's central headquarters, which they said was located beneath residential buildings in Dahieh, a southern suburb of Beirut that is considered a Hezbollah stronghold is known.

The attack shook the capital and sent thick clouds of smoke rising over the city. An NBC News team witnessed the explosion near Beirut-Rafic Hariri International Airport.

According to the Lebanese Ministry of Health, at least six people were killed and 91 injured in the attack on Nasrallah. However, the damage is extensive and it is possible that the official death toll will rise.

Both Lebanese Prime Minister Najib Mikati and Israeli Prime Minister Benjamin Netanyahu returned early from the U.N. General Assembly in New York after learning of the attack, after Netanyahu gave a speech on Friday criticizing Israel's actions in the Gaza Strip and in Lebanon and described Iran as an enemy to Israel's broader regional interests.

“There is no place in Iran that the long arm of Israel cannot reach,” Netanyahu said. “And that applies to the entire Middle East.”

In a statement after the attack, an Israeli official told NBC News that the country expected an attempt by Hezbollah to launch a major retaliatory attack.

The concern now is an escalation of war in the Middle East, including an Israeli ground operation in Lebanon, which would be “a miscalculation,” Hussain warned.

“It is better to succeed with new technologies and tactics and avoid old invasion rules because that is a proven method for failure in Lebanon based on previous attempts,” he said.

Washington, along with a number of allies, has pushed for a proposal for a 21-day ceasefire that would allow negotiations between Israel and Hezbollah in hopes of preventing an all-out war.

Husain said he believed the Biden administration, which said it had no prior knowledge of Israel's plans to attack Nasrallah, would likely make attempts to “hold Israel back,” but he believed it would first deal with “the arsenal.” the weapons held by Hamas and Hezbollah.”

“With no dismantling of Hezbollah’s military capabilities or at least promises to contain Hezbollah, I doubt that Israel can be reined in by the US government,” Husain said.