In a further escalation overnight, Israeli warplanes began striking bridges over the Litani River that link southern Lebanon to the rest of the country, destroying at least two of them, Lebanese state media said.
The Israeli military said it would target bridges on the Litani to prevent Hezbollah transferring fighters and weapons, and reiterated a warning for residents to leave the south.
The Hezbollah-Israel conflict has become the deadliest spillover of the US-Israeli war on Iran since the Iran-backed group fired at Israel in support of Tehran on March 2, with more than 900 people killed in Lebanon and one million displaced.
Strikes rattled Beirut through the night and into morning, lighting up the sky over the southern suburbs mostly controlled by the armed group Hezbollah, which have been heavily bombarded by Israel.
The escalation in central Beirut, where Israel targeted four buildings in eight hours, followed what Hezbollah described as a large rocket attack against Israel late on Tuesday. Some 100 rockets were fired, Lebanese security sources said.
The Israeli military said preventative strikes had blunted the Hezbollah attack, and that it had completed an overnight wave of strikes targeting Hezbollah infrastructure in Lebanon.
The airstrikes in Beirut hit buildings within walking distance of the downtown area that was rebuilt after the 1975-90 civil war and of the headquarters of the Lebanese government.
The targeted districts are historically mixed neighbourhoods where large numbers of Shi'ite Muslims live and Shi'ite Hezbollah and its ally the Amal Movement hold political sway.
The Israeli military statement said it had "struck assets" of a Hezbollah-run financial institution, Al-Qard Al-Hassan, in Beirut, and that the Israeli navy had targeted Hezbollah militants in the city. It did not say exactly where.
The Israeli military, in its warning posted on social media before dawn, said it would act against what it said was a Hezbollah facility in the area. There were no reports of casualties in the early morning strike on Bachoura.
The Israeli military issued no warnings before the three other strikes, the first of which tore through several floors of a building in Zuqaq al-Blat around 1.30am on Wednesday, and two floors of a building in nearby Basta around the same time.
The fourth strike, after daybreak, destroyed a floor of a second building in Zuqaq al-Blat.
No fatalities have been reported in Israel from Hezbollah rocket and drone attacks. The Israeli military says two of its soldiers were killed in southern Lebanon.
Fears are growing in Lebanon that cutting off southern Lebanon from the rest of the country could pave the way for a large-scale Israeli military operation into Lebanese territory.
