Israel has targeted a Gaza school that it says contained a Hamas compound but Gaza media reports the strike killed at least 27 people seeking shelter.
Ismail Al-Thawabta, the director of the Hamas-run government media office, rejected Israel's claims that the UN school in Nuseirat, in central Gaza, had hidden a Hamas command post.
"The occupation uses lying to the public opinion through false fabricated stories to justify the brutal crime it conducted against dozens of displaced people," Thawabta told Reuters.
Israel's military said before the strike by Israeli fighter jets, the military took steps to reduce the risk of harm to civilians.
Thursday's attack happened after Israel announced a new military campaign in central Gaza as it battles a group of fighters relying on hit-and-run insurgency tactics. Israel has said there will be no halt to fighting during ceasefire talks.
In an apparent blow to a truce proposal touted last week by US President Joe Biden, the leader of Hamas said the group would demand a permanent end to the war in Gaza and Israeli withdrawal as part of a ceasefire plan.
The remarks by Ismail Haniyeh appeared to deliver the Palestinian militant group's reply to the proposal that Biden unveiled last week. Washington had said it was waiting to hear an answer from Hamas to what Biden described as an Israeli initiative.
"The movement and factions of the resistance will deal seriously and positively with any agreement that is based on a comprehensive ending of the aggression and the complete withdrawal and prisoners swap,” Haniyeh said.
Asked whether Haniyeh's remarks amounted to the group's reply to Biden, a senior Hamas official replied to a text message from Reuters with a "thumbs up" emoji.
Since a brief week-long truce in November, all attempts to arrange a ceasefire have failed, with Hamas insisting on its demand for a permanent end to the conflict, while Israel says it is prepared to discuss only temporary pauses until the militant group is defeated.
Washington is still pressing hard to reach an agreement. CIA director William Burns met senior officials from mediators Qatar and Egypt on Wednesday in Doha to discuss the ceasefire proposal.
Biden has repeatedly declared that ceasefires were close over the past several months, only for no truce to materialise.
Last week's announcement came with far greater fanfare from the White House, and at a time when Israeli Prime Minister Benjamin Netanyahu is under mounting domestic political pressure to chart a path to end the eight-month-old war and negotiate the release of Israeli hostages held by Hamas.
Hamas, which rules Gaza, precipitated the war by attacking Israeli territory on October 7, killing around 1200 people and capturing more than 250 hostages, according to Israeli tallies. Around half of the hostages were freed in the war's only truce so far, which lasted a week in November.
Israel's military assault on Gaza has killed more than 36,000 people, according to health officials in the territory, who say thousands more dead are feared buried under the rubble.
Hamas has seen about half its forces wiped out in eight months of fighting and is relying on insurgent tactics to frustrate Israel's attempts to take control of Gaza, US and Israeli officials told Reuters.
Hamas has been reduced to 9000 to 12,000 fighters, according to three senior US officials familiar with battlefield developments, down from American estimates of 20,000-25,000 before the conflict. Israel says it has lost almost 300 troops in the Gaza campaign.
Meanwhile, a conflict between Israel and the Lebanon-based Hezbollah is threatening to escalate, with the US State Department warning against a full-blown war.
Although Biden described the ceasefire proposal as an Israeli offer, Israel's government has been lukewarm in public. A top Netanyahu aide confirmed on Sunday that Israel had made the proposal even though it was "not a good deal".
Far-right members of Netanyahu's government have pledged to quit if he agrees to a peace deal that leaves Hamas in place, a move that could force a new election and end the political career of Israel's longest-serving leader.
Centrist opponents who joined Netanyahu's war cabinet in a show of unity at the outset of the conflict have also threatened to quit, saying his government has no plan.
Meanwhile, Defence Minister Yoav Gallant said there would be no let-up in Israel's offensive while negotiations over the ceasefire proposal were under way.
"Any negotiations with Hamas would be conducted only under fire," Gallant said in remarks carried by Israeli media after he flew aboard a warplane to inspect the Gaza front.
