The prospects of a ceasefire in Gaza between Israel and Hamas have crashed again as different messages emerged on truce talks, while Israeli strikes killed at least 52 people, including children, in the war-torn Palestinian enclave.

Israeli Prime Minister Benjamin Netanyahu again vowed to bring back all hostages, "living and dead", amid confusion over the fate of a proposed 70-day ceasefire that was to see the release of 10 Israeli hostages alongside more Palestinian prisoners.

"If we don't achieve it today, we will achieve it tomorrow, and if not tomorrow, then the day after tomorrow. We are not giving up," Netanyahu said late on Monday on freeing of the captives.

Hamas said earlier it had accepted a new proposal by United States envoy Steve Witkoff, presented by mediators, but Witkoff later denied the Palestinian group had accepted.

"What I have seen from Hamas is disappointing and completely unacceptable," he told the US news outlet Axios, calling on Hamas to agree to a temporary offer that he said Israel would approve.

An Israeli official also dismissed the proposal mentioned by Hamas, saying no responsible government could accept such an agreement and rejecting the assertion that it matched the one proposed by Witkoff.

The outline of the new potential deal was revealed as Israel ramped up its offensive in recent weeks in Gaza, drawing wide condemnation.

On Monday morning, an Israeli strike on the Fahmi Al-Jarjawi School, where displaced people were sheltering, killed "at least 33, with dozens injured, mostly children", Gaza's civil defense agency spokesman Mahmud Bassal said. Another Israeli strike killed at least 19 people in Jabalia in the north.

EU chief Ursula von der Leyen denounced Israel's deadly wave of strikes as "abhorrent", during a call with Jordan's King Abdullah II on Tuesday.

German Chancellor Friedrich Merz delivered his most severe rebuke of Israel to date on Tuesday, criticizing massive airstrikes on Gaza as no longer justified by the need to fight Hamas and "no longer comprehensible".

The message, delivered from a news conference in Finland, reflects a broader shift in public opinion but also a greater willingness from top-ranking German politicians to criticize Israel's conduct.

Meanwhile, crowds of Israelis streamed through Jerusalem's Old City, where some scuffled with residents and hurled insults at Palestinians, as annual celebrations of Israel's capture of East Jerusalem take place on Monday.

The Jerusalem Day commemorates Israeli forces taking East Jerusalem during the 1967 Middle East War. Since then, Israeli settlements in the eastern part of the city, considered illegal under international law, have expanded.

Far-right Israeli minister Itamar Ben Gvir visited the Al-Aqsa Mosque compound, known to Jews as the Temple Mount, to mark the occasion. The mosque is Islam's third-holiest site and a symbol of Palestinian national identity.

Agencies and Xinhua contributed to this story.