Netanyahu vows to 'mercilessly strike' Hezbollah including in Beirut

Israeli Prime Minister Benjamin Netanyahu on Monday vowed to strike Hezbollah without mercy following a deadly drone strike on a military base in Israel, and retaliation would extend to targets in Beirut.

"We will continue to mercilessly strike Hezbollah in all parts of Lebanon –- including Beirut. All this according to operational considerations. We have proven it recently and we will continue to prove it in the days to come," he said while visiting the military base hit by a Hezbollah drone on Sunday night.

Defense Minister Yoav Gallant had told his U.S. counterpart Lloyd Austin that Israel would deliver a strong response to Hezbollah after the Lebanese armed group struck an Israeli army base killing four soldiers.

Gallant spoke to Austin overnight and "highlighted the severity of the attack and the forceful response that would be taken against Hezbollah", the minister's office said in a statement.

Israel's army chief described Monday the Hezbollah drone strike as "difficult and painful."

"We are at war, and an attack on a training base on the home front is difficult and the results are painful," Lieutenant Geneal Herzi Halevi told soldiers during a visit to the Golani Brigade training base that was hit Sunday night in the area of Binyamina, south of the city of Haifa.

Hezbollah has threatened Israel with more attacks if its offensive in Lebanon continued.

Hezbollah "promises the enemy that what it witnessed today in southern Haifa is nothing compared to what awaits it if it decides to continue its aggression against our... people," it said.

In what it described as a "complex" operation, the Iran-backed group said it had launched dozens of missiles towards Nahariya and Acre north of Haifa "with the goal of keeping Israeli defense systems busy."

At the same time, it launched "squadrons of various drones, some of which were being used for the first time, towards various areas in Acre and Haifa, where they were able to get past Israeli air defense radars without being detected" and hit the training camp in Binyamina south of Haifa, it added.

They "exploded in the rooms where dozens of officers and soldiers of the Israeli enemy were present."

After claiming the Binyamina attack, Hezbollah said it had launched missiles at a "maintenance and rehabilitation base" of the Israeli army, also south of Haifa.