Smoke rises from Israeli airstrikes in Beirut’s southern suburbs on Saturday in Lebanon. Hassan Ammar/Associated Press

BEIRUT — Lebanon’s Hezbollah group confirmed on Saturday that its leader and one of its founders, Hassan Nasrallah, was killed in an Israeli airstrike in Beirut the previous day.

A statement Saturday said Nasrallah “has joined his fellow martyrs.” Hezbollah vowed to “continue the holy war against the enemy and in support of Palestine.”

Hezbollah leader Hassan Nasrallah Hassan Ammar/Associated Press, file

Nasrallah, who led Hezbollah for more than three decades, is by far the most powerful target to be killed by Israel in weeks of intensified fighting with Hezbollah. The Israeli military said it carried out a precise airstrike on Friday while Hezbollah leadership met at their headquarters in Dahiyeh, south of Beirut.

The Lebanese Health Ministry said six people were killed and 91 injured in the Beirut strikes Friday, which leveled six apartment buildings. Ali Karki, the commander of Hezbollah’s Southern Front, and additional Hezbollah commanders were also killed in the attack, the Israeli military said.

Lt. Col. Nadav Shoshani, an army spokesperson, said the airstrike was based on years of tracking Nasrallah along with “real-time information” that made it viable.

Shoshani declined to say what munitions were used in the strike or provide an estimate on civilian deaths, only saying that Israel takes measures to avoid civilians whenever possible and clears strikes ahead of time with intelligence and legal experts.

The Palestinian militant group Hamas in a statement issued condolences to its ally, Hezbollah. Nasrallah frequently described launching rockets against northern Israel as a “support front” for Hamas and Palestinians in Gaza.

“History has proven that the resistance… whenever its leaders die as martyrs, will be succeeded on the same path by a generation of leaders who are more valiant, stronger and more determined to continue the confrontation,” the Hamas statement said.

It added that “assassinations will only increase the resistance in Lebanon and Palestine in determination and resolve.”

ISRAEL VOWS TO KEEP UP ATTACKS ON HEZBOLLAH

Israel’s chief of staff, Lt. Gen. Herzi Halevi, said Saturday that the elimination of Nasrallah was “not the end of our toolbox,” indicating that more strikes were planned.

It was not immediately clear what effect the strike would have on Hezbollah or fighting between the sides that has dragged on for nearly a year. Israel has vowed to step up pressure on Hezbollah until it halts its attacks that have displaced tens of thousands of Israelis from communities near the Lebanese border. The recent fighting has also displaced more than 200,000 Lebanese in the past week, according to the United Nations.

The military said it was mobilizing additional reserve soldiers as tensions escalate with Lebanon, activating three battalions of reserve soldiers to serve across the country. The call comes after it sent two brigades to northern Israel earlier in the week to train for a possible ground invasion.

Shoshani, the army spokesperson, said that Israel has inflicted heavy damage on Hezbollah’s capabilities over the past week by targeting a combination of immediate threats and strategic weapons, such as larger, guided missiles. But he said much of Hezbollah’s arsenal still remains intact and that Israel would continue to target the group.

“We hope this will change Hezbollah’s actions,” he said. “We have been looking for solutions, looking for a change in reality that will bring our civilians home,” referring to the approximately 60,000 Israelis who have been evacuated from their homes along the Lebanese border for almost a year. Earlier this month, Israel’s government said halting Hezbollah’s attacks in the country’s north to allow residents to return to their homes is an official war goal.

IRAN CALLS FOR SUPPORT FOR HEZBOLLAH

Iranian state television read the announcement from Hezbollah confirming Nasrallah’s death live, but there was no other immediate comment. Iranian Supreme Leader Ayatollah Ali Khamenei in a Saturday message said “the resistance movement, heading by Hezbollah, will decide the fate of the region,” in a statement read on state TV.

“All regional resistance forces are to stand by and support Hezbollah,” he said. He added that Hezbollah was strong enough to withstand Israeli attacks. Iran is the main supporter of Lebanese Hezbollah and other militant groups in the region.

Also on Saturday, Iran’s influential parliamentary committee of national security demanded “strong” response to Israel following a meeting of the committee. State TV also said people staged anti-Israeli rallies in support of Hezbollah in major cities and town across the country.

After Hezbollah’s announcement, one Iranian channel played a recitation of Quranic verses. Others put a black mourning stripe on the corner of the screen to mark his death.

A YEAR OF HOSTILITIES BETWEEN ISRAEL, HEZBOLLAH

Hezbollah started firing rockets on Israel in support of Gaza on Oct. 8, a day after Hamas militants launched an unprecedented attack on Israel, killing some 1,200 people and abducting another 250. Since then, the two sides have been engaged in cross-border strikes that have gradually escalated and displaced tens of thousands of civilians on both sides of the border.

Hostilities escalated dramatically last week when thousands of explosives hidden in pagers and walkie-talkies used by Hezbollah detonated, killing dozens of people and leaving thousands, including many civilians, with severe injuries to the eyes, face and limbs. Israel is widely believed to be behind the attack.

Israel has also killed several top Hezbollah commanders in Beirut in addition to the attack that killed Nasrallah.

A WINDOW OF OPPORTUNITY FOR ISRAEL. LEBANON

Orna Mizrahi, a senior researcher at the Tel Aviv-based think tank Institute for National Security Studies and former intelligence analyst for the Israeli military and prime minister’s office, noted that Nasrallah was sometimes a “voice of reason,” interested in engaging Israel in a war of attrition and holding the militant group back from using the full force of their formidable arsenal against Israel.

Nasrallah’s death could prompt some less senior members of Hezbollah to unleash much stronger weapons than have been used in the nearly yearlong exchange of hostilities between Hezbollah and Lebanon, she said. The biggest question mark right now, though, is how Iran will respond, said Mizrahi.

She added that Nasrallah’s death could provide a window of opportunity, while the organization is significantly weakened, for Lebanon to dilute Hezbollah’s far-reaching influence, especially in the south, that threatens to drag Lebanon into a full-scale war with Israel.

CONTINUING STRIKES ON BOTH SIDES OF THE BORDER

On Saturday morning, the Israeli military carried out more than 140 airstrikes in southern Beirut and eastern Lebanon’s Bekaa Valley, including targeting a storage facility for anti-ship missiles in Beirut suburb of Dahiyeh. Israel said the missiles were stored underground beneath civilian apartment buildings. Hezbollah launched dozens of projectiles across northern and central Israel and deep into the Israel-occupied West Bank, damaging some buildings in the northern town of Safed.

In Beirut’s southern suburbs, smoke rose and the streets were empty after the area was pummeled overnight by heavy Israeli airstrikes. Shelters set up in the city center for displaced people were overflowing. Many families slept in public squares and beaches or in their cars. On the roads leading to the mountains above the capital, hundreds of people could be seen making an exodus on foot, holding infants and whatever belongings they could carry.

At least 720 people have been killed in Lebanon over the past week from Israeli airstrikes, according to the Health Ministry.

Mroue reported from Beirut. Associated Press writers Abby Sewell in Beirut, Nasser Karimi in Tehran and Jon Gambrell in Dubai, United Arab Emirates, contributed.