Israel announced dozens of new air strikes on Hezbollah strongholds in Lebanon Tuesday, a day after 558 people, including 50 children, were killed in the deadliest bombardment since a devastating war in 2006.

Israel's overnight strikes on southern Lebanon came after it said it had killed a "large number" of militants when it hit about 1,600 suspected Hezbollah targets around the country.

Hezbollah said Tuesday it had launched volleys of missiles at Israeli military bases, hours after 180 of its projectiles and an unmanned aerial vehicle crossed into Israeli airspace, sending people in the city of Haifa running for shelter.

The Israeli military said more than 50 projectiles were fired into northern Israel in less than 10 minutes on Tuesday morning, most of which were intercepted.

It said it had carried out more strikes during the morning targeting Hezbollah infrastructure.

In Lebanon, Monday's raids killed 558 people, including 50 children and 94 women, according to Health Minister Firass Abiad.

"The vast majority, if not all of those killed in yesterday's attacks were unarmed people in their homes," he said.

The United Nations said tens of thousands of Lebanese had fled their homes since Monday, in the face of the intensifying Israeli bombardment.

"Tens of thousands of people were forced from their homes yesterday and overnight, and the numbers continue to grow," UN refugee agency spokesman Matthew Saltmarsh said, adding that "the toll on civilians is unacceptable".

"It was a day of terror," 41-year-old housewife Thuraya Harb told AFP at a makeshift centre for displaced families in Beirut after fleeing her home in south Lebanon.

"I didn't want to leave my home, but the children were scared," the mother of four said, adding that the family fled "with nothing but the clothes on our backs".

Longtime foes Hezbollah and Israel have been locked in near-daily cross-border exchanges of fire for nearly a year, since Palestinian militant group Hamas staged an unprecedented attack on Israel on October 7.

Hezbollah, which has been fighting Israel for decades, and other Iran-backed militants in the region have been drawn into the violence.

Monday's bombardment of Lebanon was by far the largest and deadliest, not just in the past year, but since the Israel-Hezbollah war in the summer of 2006.

That war killed 1,200 people in Lebanon, mostly civilians, and 160 Israelis, most of them soldiers, and devastated large swathes of Hezbollah's strongholds.

- 'Operatio