Lebanon said Israeli airstrikes killed more than 55 people on Saturday, many of them in central Beirut.
An attack in the heart of Beirut demolished a residential building and shocked the city's residents.
The strike in the working-class district of Basta killed at least 20 people and injured 66, the Lebanese Health Ministry said.
“We saw two dead people on the ground… The children started crying and their mother cried even more,” said Samir, 60, who lives in a building opposite the destroyed one.
The attack in the capital was followed by others in the city's southern suburbs, following calls from the Israeli army to evacuate.
Hamas says hostage killed in Israeli attack
A woman who was kidnapped and taken to the Gaza Strip was killed in an Israeli attack in the north of the enclave, Hamas' military wing said.
Abu Obaida, spokesman for the al-Qassam Brigades, said on Telegram that another female hostage was seriously injured in the attack, and attributed the information to the guards who had held the women captive.
The Israeli military said it could not confirm or deny the claim but that it was in contact with the family of the Israeli hostage whom Hamas said was killed.
It also said it was reviewing footage of the alleged incident released by Hamas.
The Hamas spokesman did not provide details on the identities of the two hostages.
It was also unclear exactly when the alleged attack took place.
Following Israeli military operations in the past, Hamas has often claimed that hostages had been killed.
Of the approximately one hundred hostages still under the control of Hamas and other militant groups in the Gaza Strip, only about half are estimated to remain alive.