BEIRUT — Lebanon’s Hezbollah terrorist 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.” Iran-backed Hezbollah vowed to “continue the holy war against the enemy and in support of Palestine.”

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 at 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. The Commander of Hezbollah’s Southern Front, Ali Karki, and additional Hezbollah commanders were also killed in the attack, the Israeli military said.

An army spokesman, Lieutenant Colonel Nadav Shoshani, said the airstrike was based on years of tracking Nasrallah along with “real time information” that made it viable. He said Nasrallah’s death had been confirmed through various types of intelligence, but declined to elaborate.

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

Israel vowed to keep up attacks on Hezbollah. Israel’s chief of staff, Lieutenant General Herzi Halevi, said Saturday that the elimination of Nasrallah was “not the end of our toolbox,” indicating that more strikes were planned. He said that the strike targeting Hezbollah leadership was the result of a long period of preparation.