Israel blames Hamas, saying they have chosen to keep operating among civilians.

On Monday night, Lt. Col. Peter Lerner, a spokesman for the Israeli military, said that he had not yet been able to confirm the circumstances of the attack here or who the target might have been. Colonel Lerner would not address questions about whether the target would have been considered worth so many additional deaths.

But while Israel has in the past killed Hamas members with attacks so precise that others riding in their cars have survived, in this conflict, there have been numerous instances of family homes being struck with residents inside. More and more Palestinians are accusing Israel of trying to inflict maximum suffering to demoralize Palestinians and weaken support for Hamas.

On July 13, 18 family members were killed in an airstrike on their home, and Tayseer al-Batsh, the Hamas police chief in Gaza, was severely wounded. Many other civilians have been killed in strikes on known Hamas offices or apartments that happened to be in their apartment buildings, and in strikes on homes with no obvious connection, Palestinian officials and residents say.

On Monday night, a strike hit an eight-story apartment building in downtown Gaza City — an area where Israeli officials had urged Gazans to take shelter. The building collapsed as rescue crews were inside, killing more people. The death toll, at least 13, was still being tallied.