A barrage of missiles was launched from southern Lebanon into northern Israel late Thursday.
Israeli Army Radio reported that the rockets were fired toward the Western Galilee region.
It marks the first attack since Tel Aviv assassinated top Hezbollah leader Fouad Shukr on Tuesday in Beirut.
At least seven people, including two children, were killed in that airstrike, according to Lebanese health authorities.
Israel blamed Shukr for a missile attack Saturday that killed 12 people in the Druze town in Majdal Shams in Israel-occupied Golan Heights, although Hezbollah has denied responsibility.
Shukr's assassination was followed by the assassination of Hamas political chief Ismail Haniyeh in the Iranian capital of Tehran early Wednesday in an attack blamed on Israel. Tel Aviv has not yet confirmed or denied responsibility.
Hezbollah Secretary-General Hassan Nasrallah vowed a "real response" to the strike that killed Shukr.
"We are planning a real and well-calculated response, not merely a symbolic one," Nasrallah said in a televised speech during Shukr's funeral.
"Hezbollah will resume its regular military operations against Israel on Friday, unrelated to the response to Shukr's assassination," he added.
Fears have grown of a full-blown war between Israel and the Lebanese resistance group amid a months-long exchange of cross-border fire.
The escalation comes against the backdrop of an Israeli onslaught on the Gaza Strip, which has killed nearly 39,500 victims since October, following an attack by the Palestinian resistance group, Hamas.
