At least two Hezbollah members were killed in Israeli strikes Monday while the Lebanese group claimed attacks on northern Israel.
The powerful Iran-backed group has exchanged regular cross-border fire with the Israeli army in support of ally Hamas since the Palestinian group's Oct. 7 incursion sparked the Gaza war.
But tensions have soared as Hezbollah and Iran vowed to respond after Israeli strikes last month killed Hamas political leader Ismail Haniyeh in Tehran and senior Hezbollah member Fuad Shukr in Beirut.
Hezbollah said two of its fighters were "martyred on the road to Jerusalem," the phrase it has used to refer to members killed by Israeli fire since October.
The Israeli military said air forces struck Hezbollah in the Hula area and its "military structures" elsewhere in south Lebanon.
Lebanon's official National News Agency (NNA) reported Israeli shelling and raids on several southern areas and said "enemy warplanes broke the sound barrier twice over Beirut and its suburbs ... at low altitude."
Hezbollah said it launched a "simultaneous air attack" with "explosive-laden drones" on two Israeli military positions – the Yaara barracks near the border, and a base near the coastal town of Acre, around 15 kilometers (10 miles) from the frontier.
The Israeli military said in a statement that "multiple suspicious aerial targets were identified crossing from Lebanon."
Air defenses "intercepted some of the targets, and others fell" in the Yaara area, the statement added.
Hezbollah said that the attack came "in response" to an Israeli "attack and assassination" in south Lebanon's Tyre area.
On Saturday, the Israeli military had said its aircraft "eliminated" a Hezbollah member in the Tyre area, describing him as a "commander" in the group's elite Radwan force.
Early Monday, Hezbollah said it targeted a group of Israeli soldiers "infiltrating" near the border and confronted them "with rocket weapons and artillery, forcing them to return."
Hezbollah also claimed a rocket and artillery attack on another Israeli barracks in retaliation for "Israeli enemy attacks."
Imran Riza, the United Nations humanitarian coordinator in Lebanon, said in a statement that "nearly 150,000 people continue to live in areas impacted daily by shelling and airstrikes" in Lebanon.
"Millions more are reliving painful memories of the 2006 war, traumatized by worry over the risk of further escalation," he said, referring to the last major conflict between Israel and Hezbollah.
According to the U.N.'s International Organization for Migration, the violence since October has displaced more than 110,000 people in south Lebanon.
Israeli authorities say some 100,000 people have been displaced in the country's north.
Riza added that "21 paramedics whose duties were to save others have been killed," saying "the seeming impunity with which such actions have been committed reveals a troubling disregard for international humanitarian law".
The cross-border violence has killed some 584 people in Lebanon, mostly Hezbollah members but including at least 128 civilians, according to an AFP tally.
On the Israeli side, including in the annexed Golan Heights, 22 soldiers and 26 civilians have been killed, according to army figures.
