A child was among at least 18 people killed Monday in an overnight Israeli airstrike that targeted an area near a south Beirut hospital.
Lebanon's Health Ministry revised upwards its initial toll of four on Tuesday.
Another 60 people were wounded in the strike near the Rafik Hariri Hospital, Lebanon's biggest public health facility, located a few kilometers from the city center the Health Ministry said.
The facility in the Jnah neighborhood sustained minor damage in the strike, which flattened four buildings in its vicinity, said an Agence France-Presse (AFP) correspondent in the area.
Rescuers were still searching for survivors beneath the rubble on Tuesday, said the correspondent who heard a cell phone ringing under chunks of concrete.
The strike Monday night came as Israel targeted Beirut's southern suburbs with heavy strikes following evacuation warnings.
The Ouzai neighborhood, minutes away from Jnah, was hit for the first time during the conflict, Lebanon's official National News Agency (NNA) reported.
There was no warning, however, for the area around the Rafik Hariri Hospital, which is densely populated and has seen an influx of people displaced from areas further south.
Nearly a month of all-out war by Israel has killed at least 1,489 people in Lebanon, according to an AFP tally of Lebanese Health Ministry figures.
It has displaced more than a million people, according to Lebanese authorities, with thousands crossing the border to neighboring Syria.
The strikes on Ouzai and Jnah triggered an exodus of residents, piling more pressure on shelters struggling to accommodate the displaced.
