Israeli politicians called for a resumption of the war on Gaza on Tuesday after forensics said that a body returned by Hamas hours earlier was not a captive.
The Palestinian group on Monday evening handed over the body of what it said was one of the 13 dead Israeli captives remaining in Gaza.
Anonymous sources quoted in the Israeli press later claimed that tests done by the national forensic institute showed that the coffin contained other remains of a body already returned to Israel.
The handover came as an ultimatum issued by US President Donald Trump for Hamas to return the bodies expired.
Prime Minister Benjamin Netanyahu is expected to chair an emergency meeting on Tuesday amid calls from across the Israeli political spectrum for the resumption of war and an end to the ceasefire.
Hamas has already released the last 20 living captives it held and the remains of 15 deceased ones after the ceasefire came into effect on 10 October.
The release of the dead captives has slowed in recent days, with Hamas saying it is struggling to locate the bodies under the rubble of the devastated Gaza Strip. Egypt sent in heavy equipment and specialist teams over the weekend to help with the search.
"It's time to break [Hamas's] legs once and for all," extremist national security minister Itamar Ben Gvir wrote on his Telegram channel following the reports.
"We need to take away its very existence and destroy it completely".
His far-right ally, Finance Minister Bezalel Smotrich, said he would push Netanyahu to rearrest the almost 2,000 Palestinian prisoners freed under the ceasefire deal.
Former prime minister Naftali Bennett - Netanyahu's main political rival on the ultranationalist right - called Hamas "cancer" that "must be destroyed".
Threats to resume war
The ultranationalists were joined by more centrist opposition figure Benny Gantz, who declared that the non-return of the remaining captives' bodies "cannot remain without a harsh response".
The campaign group representing the captives' family members – which previously led calls for a ceasefire inside Israel – on Monday demanded that negotiations over the second phase of the truce be suspended until the bodies are returned.
The renewed calls for war came after US president Donald Trump's 48-hour deadline for Hamas to return the bodies expired.
The US leader issued the ultimatum on Saturday afternoon on his Truth Social platform, warning that "other countries involved in this GREAT PEACE will take action" if the bodies are not returned.
Israel has accused Hamas of deliberately delaying the release of the bodies and has used this to justify repeated ceasefire violations.
The Israeli military has killed almost 100 Palestinians in several rounds of attacks during the 18-day truce and has continued to choke the supply of aid entering Gaza.
Hamas has rejected Israel's claims that it knows where the bodies are, saying that Israel's destruction of the territory has left locations unrecognisable.
"We affirm our commitment to completing the first phase of the ceasefire agreement to prevent the occupation from finding any pretexts [to resume the war]", a spokesperson for the group said on Monday.
"We are determined to hand over the bodies of the Israeli captives as soon as possible."
Knesset to vote on death penalty bill this week
Calls for the resumption of war on Gaza come Israeli lawmakers prepare to vote this week on legislation put forward by Ben Gvir that would legalise the execution of Palestinian prisoners and detainees.
The death penalty bill will be discussed by the national security committee for the second time before being put to a vote in the Knesset Plenum.
This comes despite opposition to the bill from Netanyahu and the attorney general, who has tried to stall its progress.
"The death penalty bill for terrorists is not only the flagship of Jewish Power. It is the backbone of Israeli sovereignty," said Zvika Fogel, the head of the national security committee and member of Ben Gvir's Jewish Power party.
The bill passed the national security committee in its first reading last month.