Shelling was audible and smoke rose from the surrounding area as the invading army's banner was seen by AFP above the castle, which Israeli forces famously used as a base during their previous two-decade long occupation.

Israeli Defence Minister Israel Katz said troops had captured the historic strongpoint, which commands sweeping views of south Lebanon, as they expanded their ground operations, which Lebanon's prime minister has condemned as a "scorched earth" policy.

"Forty-four years after the heroic Battle of Beaufort, and on this day commemorating the soldiers who fell in the First Lebanon War, our troops have returned to the summit of Beaufort and once again raised the Israeli flag there," Katz said, in a social media post.

"Under Prime Minister Benjamin Netanyahu and my direction, the IDF expanded the operations in Lebanon, crossed the Litani River, and captured the Beaufort Ridge -- one of the most important strategic points for defending the communities of the Galilee and safeguarding the security of our forces."

The push to Beaufort came as the Israeli military issued a sweeping evacuation order to areas south of the Zahrani River, north of the Litani and around 40 kilometres (25 miles) from the border, warning that it was targeting the Iran-backed Hezbollah armed group.

"Anyone present near Hezbollah elements, facilities, or combat means endangers their life. Any building used by Hezbollah for military purposes may become subject to targeting!" Israeli military spokesman Avichay Adraee said, in a social media post.

- 'Collective punishment' -

"A significant number of IDF ground soldiers commenced offensive operations aimed at expanding the Forward Defense Line... The operation is currently expanding to additional areas," the Israeli military said.

Lebanon's prime minister Nawaf Salam had accused Israel on Saturday of pursuing a "scorched-earth policy and collective punishment" in the south, urging a halt to the fighting and warning it was "destroying towns and villages, and forcing their inhabitants into exile".

Military delegations from both countries held security talks in Washington on Friday, with more US-brokered negotiations planned next week.

Salam said the outcome of the negotiations was "not guaranteed", but called them "the least costly path for our country and our people".

A truce to halt the fighting between Israel and Tehran-backed Hezbollah officially began on April 17, but has never been observed. Both Israel and Hezbollah accuse each other daily of violating the ceasefire and justify their attacks by the other's alleged breaches.

A US statement issued after Friday's Israel-Lebanon talks made no mention of the truce, but said the "productive military-to-military discussions" would inform next week's political meeting.

Hezbollah vehemently opposes the direct talks.

On Saturday, the Iranian-backed armed group said it launched multiple attacks targeting northern Israel and clashed with Israeli soldiers in southern Lebanon.

- 'Drone death' -

Hezbollah said it was confronting Israeli forces around the outskirts of the towns of Zawtar al-Sharqiyah, Yohmor al-Shaqif and Dibbine, adding that the troops "had not yet succeeded in taking control of the towns".

The Israeli military told AFP that more than 25 projectiles were launched from Lebanon towards Israel on Saturday, while air alert sirens sounded in the northern cities of Karmiel and Safed for the first time since the ceasefire, according to the army's Home Front Command.

Public broadcaster Kan aired footage shared on social media showing rockets falling into the sea off Israel's Nahariya, near the border, sending beachgoers fleeing.

The Israeli army also said on Sunday that one of its soldiers had been killed a day prior by a Hezbollah explosive drone, bringing to 25 the number of Israeli military deaths in Lebanon since early March.

The Lebanese health ministry says that Israeli attacks have killed more than 3,371 people since March 2.

burs-ris/dc