"Whoever harms us -- we will harm them," Prime Minister Benjamin Netanyahu said.
As the Israel-Hamas war continues, cease-fire discussions are occurring in the Middle East, with officials hoping to bring an end to the conflict.
The United States and its allies continue to plead for a cease-fire deal, with discussions set for this week.
Israel believes the Hezbollah targets in central Israel were meant to be a complex of intelligence bases and the headquarters of Mossad, the Israeli intelligence agency, just north of Tel Aviv, two Israeli security sources told ABC News.
-ABC News’ Dana Savir and Bruno Nota
At least three people were killed overnight in southern Lebanon, the Lebanese Ministry of Public Health said Sunday.
Two were killed in the village of At Tiri and one in the town of Khiam, the ministry said, adding that two additional people were injured and required hospitalization.
The United Nations agency in charge of peacekeeping in southern Lebanon called on Sunday for a cease-fire and for all sides to "refrain from further escalatory action."
"In light of worrying developments across the Blue Line since the early morning, UNSCOL and UNIFIL call on all to cease fire and refrain from further escalatory action," the agency said in a statement, referring to a demarcation line separating Israel from Lebanon.
There have been no reports of injuries on the Israeli side, according to emergency services in Israel.
-ABC News' Ghazi Balkiz, Jordana Miller and Victoria Beaule
The Israel Defense Forces on Sunday said the military was targeting Hezbollah with additional strikes in southern Lebanon.
"In the last hour, the IDF struck Hezbollah launchers in several areas in southern Lebanon to remove threats," the IDF said in a statement. "In addition, the IDF identified a terrorist cell operating in the area of Khiam in southern Lebanon. The IAF swiftly struck the terrorists."
-ABC News' Anna Burd and Victoria Beaule
Israeli Prime Minister Benjamin Netanyahu on Sunday described his country's preemptive strikes within Lebanon as a "strong action to foil the threats" raised by a potential attack by Hezbollah.
"It has eliminated thousands of rockets that were aimed at northern Israel," Netanyahu said as he convened his Security Cabinet for a meeting at 7 a.m. local time. "It is thwarting many other threats and is taking very strong action -- both defensively and offensively."
Netanyahu had earlier in the morning been managing the situation with Defense Minister Yoav Gallant from the Kirya military base in Tel Aviv, his office said. The prime minister's office released photos of the pair meeting with military officials.
"We are determined to do everything to defend our country, to return the residents of the north securely to their homes and to continue upholding a simple rule: Whoever harms us -- we will harm them," Netanyahu said.
-ABC News' Kevin Shalvey
