Hezbollah said on Thursday it fired dozens of rockets at a northern Israeli town in a "preliminary response" to the killing of 10 civilians in southern Lebanon.
The United Nations urged a halt to what it called a "dangerous escalation" of the conflict, which has played out in parallel to the Gaza war and fuelled concerns of a wider confrontation between the Iran-backed Hezbollah and Israel.
The Israeli military said it had killed a commander in Hezbollah's elite Radwan unit, his commander and another operative in a "precise airstrike" in Nabatieh in Lebannon on Wednesday, without mentioning the civilian deaths.
Israel said it had hit dozens of Hezbollah targets across the south on Thursday. Sirens sounded in northern Israel and Israeli medics and police said several rockets struck Kiryat Shmona in Israel, causing damage. There was no immediate word of casualties.
Hezbollah said it had struck Kiryat Shmona with dozens of rockets in a preliminary response to the killings in Nabatieh and Sawana. It also announced five of its fighters had been killed in Thursday's strikes.
Hezbollah has said its campaign will stop only when Israel halts its offensive on the Gaza Strip, where more than 28,000 people have been killed according to health authorities in Hamas-run Gaza.
The violence has killed more than 200 people in Lebanon, including more than 170 Hezbollah fighters, around a dozen Israeli troops and five Israeli civilians, as well as uprooting tens of thousands on both sides.