The Israeli army has escalated aerial attacks across the Gaza Strip, crushing families in the rubble of residential buildings, as health officials said dozens of Palestinians were killed overnight and medical facilities were shut down because of bomb damage and lack of power.

Across central and south Gaza, where Israel has told civilians to take shelter ahead of an expected ground offensive, there were multiple scenes of rescuers on Wednesday pulling the dead and wounded out of large piles of rubble from buildings destroyed by Israeli air attacks.

Buildings that collapsed on residents killed dozens at a time in several cases, witnesses told The Associated Press news agency. Two families lost a total of 47 members in a levelled home in Rafah, according to health officials in the enclave.

An air strike on a four-storey building in Khan Younis killed at least 32 people, including 13 members of the Saqallah family, Ammar al-Butta, a relative who survived the attack, told the AP. He said about 100 people were sheltering in the building, including many who had evacuated from Gaza City.

“We thought that our area would be safe,” he said.