Israel appears poised to launch a ground invasion of Lebanon, with hundreds of tanks massing on the border in defiance of international pleas for a diplomatic solution to the escalating crisis in the Middle East.

The Israeli army declared a closed military zone around three of its towns bordering Lebanon and began limited ground raids on Hezbollah targets on Monday (local time).

An Israeli ground offensive could occur within hours on Tuesday (AEST), according to major media outlets citing military sources.

Defence Minister Yoav Gallant met troops gathered near the border and said Israel would target Hezbollah “from the air, sea and land”.

He had also told the heads of regional councils that the “next stage” of Israel’s war on Hezbollah would “begin soon”, reports CNN.

Hezbollah’s deputy leader Naim Qassem vowed to continue fighting Israel and said the militants were ready to confront any Israeli ground invasion.

In his first public comments since the killing of Hezbollah’s chief Sayyed Hassan Nasrallah and other top commanders, he said the battle might be long.

“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,” Qassem said from an undisclosed location.

“There are deputy commanders and there are replacements in case a commander is wounded in any post.”

An Israeli ground offensive is anticipated on Tuesday, according to reports. Photo: Getty

Israeli air strikes on targets in Beirut and elsewhere in Lebanon continued, extending a two-week wave of attacks.

Several Hezbollah commanders have been killed, along with about 1000 Lebanese. A million civilians have been forced to flee their homes, according to the Lebanese government.

Nasrallah’s killing, along with blows against the organisation’s communications devices and assassination of other senior commanders, constitute the biggest hit to Hezbollah since Iran created it in 1982 to fight Israel.

Nasrallah had built it up into Lebanon’s most powerful military and political force, with wide sway across the Middle East.

Now Hezbollah faces the challenge of replacing a charismatic, towering leader, who was a hero to supporters because he stood up to Israel even though the West branded him a terrorist mastermind.

“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,” Qassem said.

Qassem said Hezbollah’s fighters had continued to fire rockets as deep as 150 kilometres 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 said, referring to the last big conflict between the two foes.

Israel said it would do whatever it took to safely return its citizens to evacuated communities on its northern border, and has not ruled out a ground invasion.

“The elimination of Nasrallah is an important step but it is not the final one. In order to ensure the return of Israel’s northern communities, we will employ all of our capabilities, and this includes you,” Israeli Defence Minister Yoav Gallant told troops at the country’s northern border.

Lebanon’s caretaker Prime Minister Najib Mikati said his government was ready to fully implement a UN 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.

Hours before Qassem spoke, the Palestinian militant group Hamas said an Israeli airstrike killed its leader in Lebanon, Fateh Sherif Abu el-Amin, along with his wife, son and daughter in the southern city of Tyre on Monday (local time).

Another Palestinian organisation said three of its leaders died in a strike in central Beirut – the first such hit inside the capital’s limits.

The Popular Front for the Liberation of Palestine said its leaders were killed in a strike on Beirut’s Kola district.

Reuters witnesses said the strike hit the upper floor of an apartment building. There was no immediate comment from the Israeli military.

The wave of Israeli attacks on militant targets in Lebanon are part of a conflict also stretching from the Palestinian territories of Gaza and the occupied West Bank, to Yemen, Iraq and within Israel itself.

The latest actions indicated Israel has no intention of slowing its offensive even after eliminating Nasrallah, who was Iran’s most powerful ally in its “Axis of Resistance” against Israeli and US influence in the region.

Iranian foreign ministry spokesperson Nasser Kanaani said Tehran would not let any of Israel’s “criminal acts” go unanswered.

He was referring to the killing of Nasrallah and an Iranian Guard deputy commander, Brigadier General Abbas Nilforoushan, who died in the same strikes on Friday.

-with AP