Hospital officials in northern Gaza say many people have been martyred in overnight Israeli air strikes.
Gazan rescue teams were quoted by media as saying that search operations began early in the morning after Israel bombed at least five buildings in Beit Lahia and Gaza City.
Local media in Gaza said that dozens of people were martyred and many are still buried in the rubble - including women and children.
Parts of northern Gaza are under Israeli siege and virtually no humanitarian aid has been delivered in 40 days, the UN warned earlier, according to the BBC.
Gazan medics say they are struggling to treat the injured, with aid agencies saying they cannot get essential supplies into the area.
Earlier this week, at least 34 people were martyred in an Israeli air strike on a five-storey residential block in Beit Lahia, the local civil defence agency said.
The agency, quoted by AFP news agency, said many of the dead were women and children.
Israel's ground offensive in northern Gaza has displaced up to 130,000 people over the past five weeks.
The UN says 75,000 people remain under siege with dwindling supplies of water and food in the towns of Beit Lahia, Jabalia and Beit Hanoun.
Last week's report by Human Rights Watch said Israel had committed war crimes and crimes against humanity by deliberately causing the mass displacement of Palestinians in Gaza.
About 1.9 million people - 90% of Gaza’s population - have fled their homes over the past year, and 79% of the territory is under Israeli-issued evacuation orders, according to the UN.
MNA