The death toll in the southern Gaza Strip is rising, as Israel steps up military strikes against Hamas.
The Israeli military said on Saturday that it is expanding operations in the Palestinian enclave.
The military also said it killed many of the Islamic group's fighters who had been disguised as civilians in the Jabalia refugee camp in northern Gaza.
Qatar-based satellite TV station Al Jazeera reported that at least 50 people died in an Israeli strike on a school run by a UN agency in the camp on Saturday.
The broadcaster also said 31 people were killed in another refugee camp in central Gaza.
The military has been urging residents in northern areas to evacuate to the south.
Al Jazeera reported that a large explosion occurred near a hospital in the southern city of Khan Younis on Sunday morning.
Israeli forces are believed to be intensifying attacks in Gaza's south. An airstrike on a housing complex reportedly caused many casualties on Saturday.
Hamas said on Saturday that more than 40 percent of the people who had been killed by the Israeli forces were residents in the south.
The group says Israeli forces are launching indiscriminate attacks on civilians in southern Gaza.