The United States has thrown its support behind Israel for its decision to delay releasing 620 Palestinian prisoners, a key term agreed upon as part of the Gaza ceasefire deal.
Israel's government was slated to release the prisoners in exchange for receiving Israeli hostages from Hamas.
But despite the hostage handover taking place on Saturday, Israel on Sunday said it would not hold up its part of the deal until Hamas committed to releasing hostages without "humiliating ceremonies".
The White House on Sunday, local time, backed Israel's decision to delay releasing the Palestinian prisoners, citing the "barbaric treatment" of Israeli hostages by Hamas.
The delay was an "appropriate response" to the Palestinian militant group's treatment of the hostages, a statement from National Security Council spokesman Brian Hughes said.
Mr Hughes said US President Donald Trump was prepared to support Israel in "whatever course of action it chooses regarding Hamas".
Hamas has made hostages appear on stage in front of crowds and sometimes speak before they were handed over. Coffins with hostage remains have also been carried through crowds.
United Nations officials have said Hamas's recent hostage handovers went against international law because they were not respectful.
Israeli Prime Minister Benjamin Netanyahu's office said the handovers "demeaned the dignity" of the hostages and were tantamount to "violations" of the ceasefire.
Ceasefire tenuous
Hamas in response has accused Israel of fabricating excuses to avoid meeting its obligations under the truce agreement, mediated by the US, Egypt and Qatar.
Basem Naim, a member of the Hamas political bureau, told Reuters the group would not engage in negotiations on the ceasefire's second phase until the Palestinian prisoners were released as agreed.
"Any talks with the enemy through mediators regarding any upcoming steps are conditional on the release of the 620 Palestinian prisoners agreed upon in exchange for the four bodies and the six Israeli captives who were freed on Saturday," he said on Sunday.
"The mediators must ensure that the enemy adheres to the terms of the agreement as stated in the agreed-upon text."
The Palestinian Prisoner's Society, a local group that supports Palestinian prisoners, said Israel was practising "state-terrorism against the prisoners and their families".
Israel and Hamas have frequently accused each other of violations since the ceasefire started on January 19 but it has so far continued to hold. Hamas at one stage said it would stop handing over hostages because of alleged Israeli breaches.
The ceasefire has brought a pause in the fighting, but prospects of a definitive end to the war remain unclear.
Both sides have said they intend to start talks on a second stage, which mediators say aims to agree the return of all remaining hostages and the full withdrawal of Israeli troops.
IDF advances in West Bank after delaying prisoner release
Israel's announcement to delay the prisoner release has abruptly put the future of the ceasefire into further doubt
Hamas had said it will release four bodies next week, completing the truce's first phase.
With Saturday's release, 25 living hostages have been returned since the ceasefire took effect in January, the bodies of four Israelis, and five Thai nationals released separately. The final four sets of remains are to be returned next week.
After that, Hamas will hold more than 60 hostages — about half believed to be alive. Hamas has said it will not release the remaining captives without a lasting ceasefire and full Israeli withdrawal from Gaza.
Also on Sunday, Israeli tanks moved into Jenin in the occupied West Bank for the first time in 23 years in what Palestinian authorities called a "dangerous escalation".
Israeli Defense Minister Israel Katz said he and Mr Netanyahu had ordered the military to "increase the intensity of the activity to thwart terrorism" in all refugee camps in the territory.
"We will not allow the return of residents, and we will not allow terrorism to return and grow," he said.
Earlier, Mr Katz said he had instructed the military to prepare for "an extended stay" in some of the West Bank's urban refugee camps. He said Israeli troops would remain there "for the coming year".
Israel launched the offensive in the northern West Bank on January 21 — two days after the current ceasefire in Gaza took hold — and expanded it to nearby areas.
Tanks were last deployed in the West Bank in 2002, when Israel fought a deadly Palestinian uprising.
ABC/Reuters/AP