Israel said it destroyed a 200-metre Hezbollah tunnel in southern Lebanon containing weapons and launchers, in a strike carried out after informing the United States.
Hezbollah condemned the strike as a "flagrant" ceasefire violation, rejected the agreement and said it reserved the right to continue defending Lebanon.
Israel said on Sunday that its military had destroyed underground Hezbollah infrastructure in southern Lebanon, carrying out a strike days after a new US-brokered security arrangement was announced between the two countries.
In a joint statement, Israeli Prime Minister Benjamin Netanyahu and Defence Minister Israel Katz said the operation targeted a 200-metre (656-ft) tunnel in the town of Majdal Zoun. According to the statement, Washington had been informed in advance of the strike.
Israeli authorities said the tunnel contained hundreds of weapons and launch systems.
The operation came two days after Lebanon and Israel agreed to a US-mediated framework intended to reduce tensions along the border. Under the arrangement, Israel is expected to withdraw in phases from parts of southern Lebanon while the Lebanese army expands its deployment. However, Israeli forces would be allowed to remain in an enlarged security zone for the time being.
The strike also followed earlier Israeli military operations in southern Lebanon. Hours before the tunnel attack, Israel said it had targeted Hezbollah fighters carrying rocket-propelled grenades and struck a rocket launcher in the Nabatieh area.
Hezbollah condemned the attacks early on Monday, calling them a "flagrant" violation of the ceasefire, which the group said it had respected so far. It added that it was closely tracking violations and reserved the right to "defend its homeland and people."
Hezbollah leader Naim Qassem has already rejected the new security framework, describing it as a surrender to Israel and reiterating that the group would continue armed resistance.
Netanyahu said in Sunday’s statement that Israeli forces would remain inside the security zone in southern Lebanon and would "continue to destroy terrorist infrastructure, remove threats from the northern communities, and safeguard the security of Israel's citizens."
The conflict, unfolding alongside the wider confrontation involving Iran, has displaced more than one million people in Lebanon. Hezbollah and Iran have argued that Washington committed to ending hostilities in Lebanon under the memorandum of understanding reached two weeks ago to bring the broader conflict to a halt.
