The official Palestinian news agency said at least 50 people were killed on Monday in an Israeli air strike that hit two schools sheltering displaced people in the north of the Gaza Strip.
The reported attack took place as Israeli bombs also rained down on southern areas of the enclave and Israeli troops and tanks pressed a ground campaign against Hamas militants in that sector.
The strike hit the Daraj neighbourhood in Gaza City, the WAFA agency said. It was not immediately possible to verify the report independently, and a spokesperson for the Israeli army said it was looking into the report.
It came as Gaza's health ministry said that at least 15,899 Palestinians, 70 percent of them women or under 18s, have now been killed in Israeli air and artillery strikes on the enclave since Oct 7. Thousands more are missing and feared buried in rubble.
Earlier on Monday, Israel ordered Palestinians to leave parts of Gaza's main southern city, Khan Younis. But residents said that areas which they had been told to go to were also coming under fire.
Israel's military posted a map on social media platform X on Monday morning with around a quarter of Khan Younis marked off in yellow as territory that must be evacuated at once.
Three arrows pointed south and west, telling people to head towards the Mediterranean coast and towards Rafah, a major town near the Egyptian border.
Desperate Gazans in Khan Younis packed their belongings and headed towards Rafah. Most were on foot, walking past ruined buildings in a solemn and silent procession.
But the head of the United Nations agency for Palestinian refugees in Gaza (UNWRA), Thomas White, said people in Rafah were themselves being forced to flee.
"People are pleading for advice on where to find safety. We have nothing to tell them," he said on X.
Israel launched its assault to wipe out Hamas, which rules Gaza, in retaliation for an Oct 7 cross-border attack by its gunmen. They killed 1,200 people and seized 240 hostages, according to Israeli tallies.