Israeli strikes on Lebanon Monday killed 492 people, including 35 children and 58 women, Lebanese authorities said.
The Israeli military warned residents in southern and eastern Lebanon to evacuate ahead of its widening air campaign against Hezbollah.
Thousands of Lebanese fled the south, and the main highway out of the southern port city of Sidon was jammed with cars heading toward Beirut in the biggest exodus since 2006.
Lebanon's health ministry said the strikes killed 356 people, including 24 children and 42 women, and wounded 1,246 people.
The death toll far surpassed that of Beirut's devastating port explosion in 2020, when hundreds of tons of ammonium nitrate stored in a warehouse detonated, killing at least 218 people and wounding more than 6,000.
In a recorded message, Israeli Prime Minister Benjamin Netanyahu urged Lebanese civilians to heed Israeli calls to evacuate, saying "take this warning seriously."
"Please get out of harm's way now," Netanyahu said. "Once our operation is finished, you can come back safely to your homes."
Israel's military spokesman, Rear Adm. Daniel Hagari, said Israeli warplanes had struck 1,300 Hezbollah targets Monday, destroying cruise missiles, rockets laden with heavy explosives, long- and short-range rockets and attack drones.
He said many were hidden in residential areas, showing photos of what he said were weapons hidden in private homes.
"Hezbollah has turned southern Lebanon into a war zone," he told a news conference.
Israel estimates Hezbollah has some 150,000 rockets and missiles, including guided missiles and long-range projectiles capable of striking anywhere in Israel.
Earlier Monday evening, the Israeli military said it had carried out a targeted strike in Beirut but did not give details.
Lebanon's state-run National News Agency reported southern Beirut's Beir al-Abed neighbourhood was hit with three missiles. Hezbollah's Al-Manar TV said six people were wounded.
Lebanese Health Minister Firass Abiad told a news conference the earlier strikes hit hospitals, medical centres and ambulances.
The government ordered schools and universities to close across most of the country and began preparing shelters for the displaced.
Some strikes struck residential areas in the south and the eastern Bekaa Valley. One hit a wooded area as far away as Byblos in central Lebanon, more than 80 miles (130 kilometers) from the border north of Beirut.
The military said it was expanding the airstrikes to include areas of the valley along Lebanon's eastern border with Syria.
Hezbollah has long had an established presence in the valley, where the group was founded in 1982 with the help of Iran's Revolutionary Guards.
Israel's military chief, Lt. Gen. Herzi Halevi, said Israel was preparing its "next phases" of operations against Hezbollah, and that its airstrikes were "proactive," targeting Hezbollah infrastructure built over the past 20 years.
Halevi said more details would be released in the near future, and that the goal was to allow displaced Israelis to return to their homes in northern Israel.
Meanwhile, Hezbollah said it fired dozens of rockets toward Israel, including at military bases. It also targeted for a second day the facilities of the Rafael defence firm, headquartered in Haifa.
