Israel said its military attacked Hezbollah targets in Beirut's southern suburbs on Sunday after the group fired into Israeli territory.
The Lebanese state news agency said two people were killed.
The Israeli military said earlier that Hezbollah had launched three projectiles towards communities in northern Israel, calling it a blatant ceasefire violation.
"The IDF has now attacked targets of the Hezbollah...in the Dahiyeh neighbourhood of Beirut, in response to Hezbollah's firing into Israeli territory," a joint statement by Prime Minister Benjamin Netanyahu and Defence Minister Israel Katz said.
There was no immediate comment from Hezbollah on the Israeli statement, but the group said it launched missiles and drones towards Israeli troops in southern Lebanon.
Last week, an Israeli strike on Dahiyeh triggered an exchange of fire between Israel and Iran that threatened to derail a US-Iran deal that would end the wider war.
Washington and Tehran appear to be getting closer to a deal to end the more than three-month-long conflict, with US and Pakistani leaders forecast a signing on Sunday.
Iran has long made the cessation of fighting in Lebanon a condition for any wider agreement with the United States.
Lebanese security sources said the attack on Dahiyeh appeared to be a targeted strike with two missiles.

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