"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 statement said, adding its forces had crossed the Litani river.

Prime Minister Benjamin Netanyahu announced on Friday that Israeli forces had crossed Lebanon's Litani River, which runs around 30 kilometres north of the countries' shared border.

A truce to halt the fighting between Israel and Tehran-backed Hezbollah officially took effect on April 17, but has never been observed.

Both Israel and Hezbollah accuse each other of violating the ceasefire and justify their attacks by the other's alleged breaches.

On Sunday, the Israeli military said it launched an operation "a few days ago" in the Beaufort Ridge and Wadi al-Saluki area in southern Lebanon, "with the aim of removing direct threats to the communities of the Galilee Panhandle and Metula, and as part of ongoing efforts to strengthen operational control in southern Lebanon".

Lebanon's Prime Minister Nawaf Salam accused Israel on Saturday of pursuing a "scorched-earth policy" in his country's south.

The Lebanese health ministry says that Israeli attacks have killed more than 3,371 people since March 2, when Hezbollah drew Lebanon into the Middle East war.