"Over the past 24 hours, IDF forces operating south of the Yellow Line in southern Lebanon identified terrorists who violated the ceasefire understandings and approached the forces from north of the Yellow Line in a manner that posed an immediate threat," the military said, referring to such a line for the first time since a ceasefire came into effect.

"Immediately after identification and in order to eliminate the threat ... forces attacked the terrorists in several areas in southern Lebanon," it said, noting that the military was authorised to take action against threats, despite the ceasefire.

"Actions taken in self-defence and to remove immediate threats are not restricted by the ceasefire," the military said.

Since a ceasefire came into effect in Gaza on October 10, the Palestinian territory has been split by a "Yellow Line", the de facto boundary dividing Gaza into two zones: one under Israeli military control and one under Hamas control.

Israel and Lebanon agreed to a 10-day ceasefire on Thursday in order to negotiate an end to six weeks of war between Israel and the Iran-backed group Hezbollah.

The war saw massive Israeli airstrikes across Lebanon and also a ground invasion in the south.

Lebanese authorities say the war that began on March 2 has killed nearly 2,300 people, and caused widespread devastation in southern towns and cities such as Nabatiyeh.

Hezbollah halted military operations after the ceasefire came into effect, but warned that it was keeping its "finger on the trigger" in case Israel violated the truce.

Lebanese President Joseph Aoun said on Friday that "direct negotiations" with Israel "are crucial", and that the government aims to "consolidate a ceasefire, secure the withdrawal of Israeli forces from the occupied southern territories, recover prisoners, and address outstanding border disputes".

US President Donald Trump has said the United States had "prohibited" Israel from bombing Lebanon following the ceasefire deal, adding that Washington would work with Lebanon to "deal with" Hezbollah.

But Israel has not "yet finished the job" on Hezbollah, Prime Minister Benjamin Netanyahu said, vowing to press on with the Lebanese militant group's "dismantling" just hours after the truce came into effect.