"Sirens have sounded in several areas of northern Israel after projectiles were fired from Lebanon," the Israeli military wrote on Telegram.
Hezbollah, an ally of Iran, said over the weekend that the movement had a "duty" to support Iran after the Israeli and US offensive, but confirmed attacks by the group were carried out only on Monday.
Hezbollah said in a statement that it fired "several rockets and a swarm of drones" at Israel to defend Lebanon and to avenge the death of Iran's Supreme Leader, Ali Khamenei.
The Israeli military says it is carrying out airstrikes "across Lebanon" against Hezbollah targets overnight. Explosions were heard in suburbs of the capital, Beirut.
Lebanese Prime Minister Nawaf Salam condemned the attacks claimed by Hezbollah.
"Regardless of who is behind it, the rocket fire from southern Lebanon is an irresponsible act that endangers Lebanon's safety and security and gives Israel pretexts to continue its attacks on the country," wrote Salam on X.
