Hezbollah leader Hassan Nasrallah has been killed after airstrikes in Beirut as they chillingly vowed to “continue the holy war against the enemy”.

Lebanon’s Hezbollah group confirmed on Saturday that its leader and one of its founders, 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”.

It is the most significant blow to the Lebanese militant group after months of fighting. Nasrallah is by far the most powerful target to be killed by Israel in weeks of intensified fighting with Hezbollah. The military said it carried out a precise airstrike on Friday while Hezbollah leadership met at their headquarters in Dahiyeh, south of Beirut.

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. He said that the strike targeting Hezbollah leadership was the result of a long period of preparation.

The Lebanese Health Ministry said six people were killed and 91 injured in the 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.

The Israeli 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.

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

Shoshani 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.

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

Shoshani 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.

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.