Hezbollah's deputy leader has pledged to continue fighting Israel and signaled readiness for a prolonged conflict following the loss of much of the group's top leadership, including its chief, Hassan Nasrallah.

In a first speech since Nasrallah's assassination by Israel, Naim Kassem said in a televised statement Monday that if Israel decides to launch a ground offensive, Hezbollah fighters are ready to fight and defend Lebanon.

"We will face any possibility and we are ready if the Israelis decide to enter by land and the resistance forces are ready for a ground engagement," he said in an address from an undisclosed location.

As deputy secretary-general, Kassem is now the acting leader of Hezbollah until a replacement for Nasrallah is chosen.

"We will choose a secretary-general for the party at the earliest opportunity...and we will fill the leadership and positions on a permanent basis," Kassem said.

Qassem said Hezbollah members had continued to fire rockets as deep as 150 kilometers (93 miles) into Israeli territory and were ready to face any possible Israeli ground incursion.

"What we are doing is the bare minimum ... We know that the battle may be long," he said. "We will win as we won in the liberation of 2006 in the face of the Israeli enemy," he added.

Israel, meanwhile, says it will do whatever it takes to return its citizens to evacuated communities on its northern border safely. It has not ruled out a ground invasion and its troops have been training for it.

Israeli strikes have killed Nasrallah and six of his top commanders in the last 10 days, and have hit what the military says are thousands of targets across large parts of Lebanon.

Over 1,000 people have been killed in Lebanon, nearly a quarter of them women and children, according to the Health Ministry, and the government says the fighting may have displaced up to a million people.

Kassem added that despite the killing of Hezbollah’s top military commanders over the past months, Hezbollah now is relying on new commanders.

"Israel was not able to affect our (military) capabilities," Kassem said. "There are deputy commanders and there are replacements in case a commander is wounded in any post."

Lebanon's caretaker Prime Minister Najib Mikati said on Monday his government was ready to fully implement a U.N. resolution that had aimed to end Hezbollah's armed presence south of the Litani River as part of an agreement to stop the war with Israel.

Mikati said the Lebanese army could deploy south of the river, which lies about 30 kilometers from the country's southern border.

Central Beirut targeted

Before he spoke, an airstrike leveled an apartment building and killed three Palestinian resistance members in central Beirut early Monday, as Israel appeared to send a clear message that no part of Lebanon is out of bounds.

As recently as two weeks ago, such a strike, outside of the main areas where Hezbollah operates and next to a busy transportation hub, would have been seen as an escalation and likely followed by a long-range Hezbollah strike into Israel. But the unspoken rules of the long-running conflict, and Hezbollah's ability to respond, are no longer clear.

Israel has not claimed Monday's strike but is widely assumed to have carried it out.

It's possible that Hezbollah is holding back to avoid an even bigger escalation, including a threatened Israeli ground invasion. But the armed group might also be in disarray after Israeli intelligence apparently penetrated its highest levels.

The strike early Monday killed three members of the Popular Front for the Liberation of Palestine, a small, leftist faction that has not been meaningfully involved in months of fighting between Israel and Hezbollah.

In the past week, Israel has frequently targeted Beirut's southern suburbs, where Hezbollah has a strong presence – including the massive strike on Friday that killed Nasrallah – but had not hit locations closer to the city center.

Hezbollah began firing rockets, drones and missiles into northern Israel after Hamas' Oct. 7 incursion from Gaza into Israel sparked the war there.

Hezbollah and Hamas are allies and both supported by Iran, and Hezbollah said it would continue the attacks in solidarity with the Palestinians until there was a cease-fire in Gaza.