That conflict marked the deadliest spillover of the Gaza war, and a blistering Israeli offensive after months of cross-border exchanges of fire wiped out Hezbollah's top commanders, many of its fighters and much of its arsenal.
Hezbollah denied responsibility for Saturday's strikes, saying it had "no link" to the rocket launches and that it remained committed to the ceasefire. No group claimed responsibility for the attack.
An Israeli official said the identity of the group which fired the rockets had not been confirmed. Six rockets were fired, the official said, three of which crossed into Israel and were intercepted.
Two waves of Israeli strikes killed three people in Bint Jbeil and Touline, as well as five in the port city of Tyre, all in southern Lebanon, according to Lebanon's state news agency, which cited health authorities.
Saturday's exchanges were the first since Israel in effect abandoned a separate ceasefire in Gaza with Palestinian militant group Hamas, an ally of Hezbollah, both backed by Israel's arch-foe Iran.
Later in the day, the Israeli military announced a second round of strikes on what it said were Hezbollah targets.
"We expect Lebanon to take care of its part of the agreement," Ophir Falk, Israeli Prime Minister Benjamin Netanyahu's foreign policy adviser, told Reuters.
"The IDF will do whatever it takes to enforce the ceasefire and to make sure that our civilians can get back home safely and securely," Falk said.
Israel's military said early on Saturday it had intercepted three rockets launched from a Lebanese district about six kilometres north of the border towards the Israeli town of Metula, the second cross-border launch since the US-brokered ceasefire in November ended fighting.
In retaliation, Netanyahu ordered the military to "act forcefully against dozens of terror targets in Lebanon".
Israel's military said it had struck dozens of Hezbollah rocket launchers and a command centre from which the group's militants had been operating, in southern Lebanon.
Lebanon's state news agency reported Israeli airstrikes and artillery barrages in the country's south, including border towns and hilltops around eight kilometres inside Lebanese territory.
In Gaza, health authorities said five Palestinians had been killed by Israeli fire, including a child, in incidents in Beit Lahiya and Gaza City in the north of the enclave.
The Israeli military said a number of militants in a vehicle were identified approaching its troops in northern Gaza who "posed a threat to them" and the military struck them.
An Israeli airstrike on the city of Rafah, which abuts Gaza's southern border with Egypt, killed two Palestinians, Gazan medics said. Israel's military said it had struck militants in the area.
Under the November ceasefire deal, Hezbollah was to have no weapons in southern Lebanon, Israeli ground troops were to withdraw and Lebanese army troops were to deploy into the area.
The agreement specifies that Lebanon's government is responsible for dismantling all military infrastructure in southern Lebanon and confiscating all unauthorised arms.
President Joseph Aoun ordered the Lebanese army to secure "any violation" that could threaten stability in Lebanon. The army said it had found and dismantled three "primitive rocket launchers" in the south.
Netanyahu said Israel was holding Lebanon's government responsible for "everything taking place within its territory" and that Israel would not allow any harm to its citizens and sovereignty.
The United Nations peacekeeping force in Lebanon said it was alarmed by the "volatile" situation and that any further escalation could have "serious consequences for the region".
Prime Minister Nawaf Salam warned of a renewal of military operations in the south of Lebanon, adding: "All security and military measures must be taken to show that Lebanon decides on matters of war and peace".
The ceasefire ended Israel's intense bombardment and ground operations in Lebanon and Hezbollah's daily rocket barrages into Israel. Each side has accused the other of failing to implement the deal in full.
